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Mite Histiostoma maritimum

The mite Histiostoma maritimum Oudemans 1914 is a member of the mite family Histiostomatidae (Astigmata, Acariformes). Oudemans discovered the mite based on its deutonymph only from a Dutch island. The German acarologist R. Scheucher found the species in 1957 in mud at the riverside of Regnitz and for the first time could rear H. maritimum and was able to redescribe it by its adult stages, especially females look morphologically conspicuous due to a sclerotized cuticula shield around its copulation opening. She reared her specimens on potatoes, mud and bran, but describes that her cultures did not grow well.

Phoretic carrieres (hosts) are beetles of genus Heterocerus, some carabids and according her findings also rarely some staphylinids.

I discovered H. maritimum between 2000 and 2004 repeatedly in sapropel around ponds in an old gravel pit area in Berlin, forest Grunewald, named „im Jagen 86“. They were mainly attached to the beetles Heterocerus fenestratus and Heterocerus fusculus, but could regularly also be found on the carabids Elaphrus cupreus and Bembidion sp.. I could several times rear the mites, like Scheucher hardly on potatoes, but quite well on cadavers of their carriers. I thus assumed a so called necromenic life-strategy for H. maritium. This means that a phoretic stage ascends a carrier, but never leaves, instead it awaits the carrier’s natural dead to develop on its cadaver (published in my phd thesis, online, 2004).

I never before published the full set of SEM photos from these former times at the beginning of my research carrier (except of my article about host specificity). In this explicite photo publication here on my homepage, I herewith publish SEM-photographs, objects sputtered with gold, which seemingly are still unique to science.

I do not know about any subsequent research on this mite worldwide. Reason is that modern science cannot be justified by gaining knowledge. In the past decades a good reason to get research funded, today not applied enough for any support. This is why I was forced to focus on bark beetle and ant nest inhabiting mites only within the last 10 years.

 

 

Adults of Histiostoma maritimum: A left male, right female, B, C, copulation opening, D dorsal view to female with mouthparts and copulation opening

 

 

Systematics: H. maritimum shares morphological characters of deutonymph (setation, apodemes) and adults (mouthpart details, shape of Digitus fixus) with species like Histiostoma feroniarum, H. insulare, H. litorale, H. palustre, H. polypori, H. myrmicarum. This might indicate a separate clade, but according to the old findings in my phd thesis, also a paraphyletic grouping including these species is thinkable.

 

Copyrights Stefan F. Wirth, 10 June 2020

 

 

Systematics and biology of termites and about their phoretic associations

They live in eusocial communities, but are not closer related to ants or bees. Termites belong to the cockroaches.

 

Queen, king and castes

 

Usually one queen and one king are reproductive and act as heads of the nest. The different work fields of a nest are executed by infertile specimens, which can show very different and specialized body shapes. The diversity of different castes is in phylogenetically „primitive“ taxa lower than in „higher developed“ termite groups.

 

As example specimens of a deadwood species from Italy

 

This species was found in deadwood of a small forest in Portici (Gulf of Naples, Italy) and might represent the taxon Kalotermitidae. This taxon branches off rather basically  in the systematic tree of termites. Nest work can be taken over by nymphs of later alates.

 

deadwood-termites from Italy, Youtube: copyrights Stefan F. Wirth, April 2020

 

 

How is wood-eating possible?

 

Wood eating termites bear bacteria and protozoans  in their digestive tracts, which perform the digestion of cellulose.

 

Evolution, sister taxon and endosymbionts

 

Termites (Isoptera) evolved within the cockroaches (Blattodea). According to modern systematics (e.g.  Beccaloni & Eccleton, 2011) the cockroach taxon Cryptocercidae is the sister-clade of the termites. But there are controversial theories existing.

According to such reconstructions, the last common ancestor of cockroach taxon Cryptocercidae and termites possessed bacterial and protozoan endosymbionts. Molecular data proved that endosymbionts in both groups are closely related to each other. The last common ancestor of both groups showed in case of their indeed sister-group-relation a tendency towards social communities. Cryptocercidae live temporarily in bigger groups together with their offspring.

 

Subsocial lifestyle in Cryptocercidae

 

Cockroaches of the Cryptocercidae as putative sister taxon of termites live inside galleries in deadwood and feed on wood fibres. At least one parent and its nymphs live subsocially inside their galleries. Cryptocercidae adults and nymphs groom each other, and parents feed juveniles with wood fragments afer these had passed their anus openings.

 

According to recent systematic/ phylogenetic reconstructions the Kalotermitidae belong to the basically branching termite groups. Such basic groups of termites still show a low diversity of castes only.

 

Associates, commensalism and phoresy

 

Like ants or bees, termites share their nests regularly with associates of other groups of animals,

often mites and nematodes. Some of these organisms use termites as carriers for a transport over bigger distances. details of such associations between insects and mites are not well studied yet. But carrier-passenger-situations with transfer („taxi“-) purposes are called phoresy. Phoresy ist mostly considered as a neutral association between different organisms and is thus interpreted as commensalism. Commensalism is differed from strategies like parasiticm or symbiosis and requires that two organisms in association do not harm or noticeably benefit each other. The term commensalism often includes associations, in which the true context for both organism partners is simply not understood yet.

 

Not yet mites of the Gamasina (Parasitiformes) were reared in greater numbers out of my Italian termite substrate. They might represent phoretic cohabitants of those termites. Other mite species of different mite groups (Parasitiformes and Acariformes) were only found in smaller numbers and died out too quickly for collections and determinations under my culture conditions, unfortunately already before the beginning of my shootings. seemingly microclimatic conditions had become too unfavorable.

 

Copyrights Stefan F. Wirth, Berlin 2019 – 2020, all rights reserved

Host specificy, host change and intermediate hosts in different organisms – with special reference to viruses and Sars-CoV-2

We recently read a lot about the pandemic consequences of infections with the new corona virus Sars-CoV-2, most are medical issues, hygienic advises and information about political reactions in different countries worldwide. But there is not much known about the biological host reservoir, putative intermediate hosts and how the human infections might be explained. It is a normal lack of information, because the scientific research about topics, being generally new to science, is time costing, especially, when life strategies and the population dynamics of organisms a concerned. Organisms? Viruses are per definitionem not considered organisms, because they lack important aspects, which characterize real life: they cannot reproduce on their own power, they do not have an own metabolism, no ingestion, no excretion. But they are organic and show traces of life by possessing a genome, which might indicate that they evolved from living cells. Viruses represent a diverse group of protein bodies containing nucleic acid, either DNA or RNA.

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New corona virus Sars-CoV-2, Wikipedia: CDC/ Alissa Eckert, MS; Dan Higgins, MAM / Public domain

Viruses in general, host specificity, host increase, host change

For reproduction viruses depend on living host cells, which they reprogram by inserting their virus genome into the cell’s genome in order to stimulate the forming of a number of virus copies, all that happening on cost of the host cell’s life. Thus viruses need to be named parasites as they harm their hosts to their own advantage. Different groups of viruses attack different kinds of cells using in detail different methods to enslave their host cells. There are plant viruses, viruses associated with bacteria (named bacteriophages) and animalistic viruses. They all show characters, which are typical for parasite – host – relationships. Parasitic partners of any kind of host – parasite – relationship can be exclusively associated with one host species only (host specificity) or a limited group of systematically closely related hosts, while others can have a wider range of different host species. The latter generally might have evolved out of the former, although also the opposite direction is thinkable. When former host-specific parasites make themselves one or even several further hosts accessible, then this phenomenon is named host-increase (Wirtserweiterung). In case an new host was infested as permanent host, while the former host is given up, then a so called host change (Wirtswechsel) happened. The same term is also used in a different context, namely when a parasite requires in its development a change between different hosts.

Host specificity: A parasite (or an organism with similar life-strategy) is associated with one host only, which requires a specialization and a competition between host evolution and parasite evolution (coevolution). This strategy needs to be separated from generalism, which means that a parasite has a very wide range of not related regular main hosts. Host specificity is more common than generalism. But this also depends on definitions. I herewith define the association with one main host species only as host specificity. But I furthermore consider host specificity also given, when parasite-host relations are specific on a higher taxonomic level, for example, when certain closely related genera of parasites are specialized for certain closely related genera of hosts. This part of my definition has variable borders. In the chapter after next, I describe the parasitic case of the trematode Leucochloridium paradoxum, whose main hosts are represented by different systematically not closer related bird species. A host specificy on the level of birds in general (Aves), then present in only some species with similar food preferences might already need to be named a limited generalism.

Obligatory host change in ticks and lifstyle-change in water mites

Some parasites need several hosts to be enabled to finish their life-cycles. This is another context, in which the German term „Wirtswechsel“ (host change) is used. In that kind of parasite – host – association, the host change is often obligatory, meaning that the parasite cannot survive in the absence of one of the required hosts. The castor bean tick Ixodes ricinus represents a parasite, which needs a host change to successfully go through its full development until adulthood, but there is a wider range of suitable hosts, as intermediate host and as final host. Thus the tick is a generalist with obligatory host change. Water mites (Hydrachnidia) are parasitic as first nymphs (juvenile instar, usually named „larva“) and predators as older nymphs and adults. A host specificity of „larvae“ can appear, but a wider range of host species is common. These mites perform a life style change during their development.

Intermediate host, for example in the parasitic flatworm Leucochloridium paradoxum

An example for a parasite, obligatory requiring a specific intermediate host, is the flatworm Leucochloridium paradoxum („green-banded broodsac“, Trematoda, Platyhelmintes), whose larvae (miracidium) need to infest snails of the genus Succinea. This trematode parasite is host specific for a genus of snails, while there is no specificity for their main hosts. They parasite birds, but infest different bird species, which are not closer related to each other, such as finches, the crow family Corvidae or woodpeckers. Although there is a main host specificity on the very high taxonomic level of Aves, the use of the term (limited) generalism might in this case even be appropriate. Inside the smail’s midgut gland, miracidia (larvae) modify into another larva-form, named cercaria, which invade the liver, where they form so called sporocysts, sac-shaped muscular tubes, which grow through the entire snail host until they reach the snail’s tentacles, which they fill up with their tube-shaped bodies entirely. Lastly the snail is unable to retract her swollen organs. The snail tentacles are now well visible as conspicuous greenish stripes, pulsating permanently. The sporocysts as larval stage of this trematode parasite do even more than only increasing the visibility of the snail for bird predators, which represent the worm’s final host. They additionally manipulate the nervous system of the snail so far that the snail performs an unusual behavior and moves towards very well exposed elevated areas, such as leaves of adjacent plants. Thus the probability to be eaten by birds is remarkably increased.

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Parasite Leucochloridium paradoxum, sporocysts inside the tentacles of a snail of genus Succinea, Wikipedia: Thomas Hahmann / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Host specificity on humans with side-hosts and coevolution with the ancestor line of Homo sapiens: skin mite Sarcoptes scabiei

An interesting example of a host specificity with numerous side-hosts and even an additional host-increase is the skin parasitic mite Sarcoptes scabiei (also named the „seven-year itch“). It was originally exclusively specific for Homo sapiens and accompanied mankind over its entire evolution (e. g. J. R. H. Andrew’s Acarologia, 1983). Systematical relatives of that mite species can only be found within the Great Apes. Originating from the recent Homo sapiens, S. scabiei conquered the human’s domestic animals, such as dogs or bovine animals within long-term periods, in which humans and their domestic animals had shared the same buildings or even rooms. Domestic animals may transfer the mite-parasite subsequently to wild animals. In case main host (humans) and side hosts (domestic animals, wild animals) can supply everything, which the parasite needs for its development without the necessity to leave its host specimen, one might speak about real hosts. In case side hosts cannot supply the necessary basic equipment, they represent either intermediate hosts or dead-end hosts. It can for example be discussed, whether dogs might in fact be dead-end hosts, as the skin disease can harm them under certain conditions to dead.

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Mite Sarcoptes scabiei (Astigmata, Acariformes), Wikipedia: Kalumet / CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/)

Host increase due to the globalisation and human economic interests: example honey bee parasite Varroa destructor (mite)

Another example of a former host specificity on a species‘ level with host increase is the mite Varroa destructor (Parasitiformes, Mesostigmata). It was originally specific for the Eastern honey bee Apis cerana. The mite could only switch over to the Western honey bee Apis mellifera due to a human influence: Men transferred A. mellifera for economic reasons to the natural habitats of A. cerana in Eastern Asia, were it got infected by the mite V. destructor. A subsequent transfer of the Western honeybee back home established the mite parasite in Western countries. As A. mellifera colonies are much more harmed by V. destructor than its original host, our honey bee must be considered as an intermediate case between a new host and a dead-end host. Human international traffic enabled this host-increase primarily, although there are areas between Afghanistan and Iraq, where both bee species coexist due to natural distribution. But there is an almost insurmountable (allopatric) desert border between the population of both species of about 360 to 600 kilometers, although there are evidences for bees rarely surmounting this border. Thus a natural mite transfer between closely related bee species might have happened additionally. Species of animals, plants, fungi or bacteria and even viruses, which successfully established new (additional) living spaces are named neobiota or alien species.

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Mite Varroa destructor, Wikipedia: The original uploader was Tullius at German Wikipedia. / Public domain

Can viruses as non-living genome possessing lumps be subject of evolution and complex host – parasite relationships?

Can this high complexity of modes of parasite – host – relationships in living organisms also be found in virus – host – relationships, although viruses do not represent living organisms at all according to biological definitions? The answer is yes, because viruses do not only share a genome with living cells, but based on this genome even are subject to the mechanisms of evolution. And evolution was the most important factor in all the mentioned complex parasite – host – interactions.

Parasitism versus mutualism or harming the host or not harming the host

Two different life-strategies with similar mechanisms as organism – to – organism associations

Are there other organism – to – organism relationships, being subject to a similar complexity than found in parasites with their hosts? Yes, a superordinate term for other close associations between different organism species is mutualism. While parasites need to harm their hosts by using them as final living-sources, mutualists are considered to practice a more neutral host contact, which per theoretic definition means that nobody harms anybody. But the assumption of a neutrality is in fact an artificial construct, as in detail it can come out that some of these organism associations represent unrecognized parasite-relationships, while in other cases a benefit for both partners (symbiosis) or for one partner only might be discovered in future studies. At least so called mutualists share as a feature that harmfulness or benefit are not easily noticeable.

Phoresy: taking a ride on a taxi-host as example of mutualistic relationships

An example for a more neutral organism, at least not harming association is called phoresy. It is often performed by nematodes and mites. These tiny organisms take a ride on bigger animals in order to become carried from one habitat to another. This „taxi-association“ is considered being of advantage for the phoretic part and harmless for the carrier (in English also often named host). But there are seeming phoretic interactions known, which based on developing technical scientific standards could be identified as unusual cases of parasitism. An example is a phoretic instar of an astigmatid mite (Astigmata, Acariformes), which as all phoretic instars within this big mite clade has no functional mouth, but sucking structures to fix itself to its host. This specific mite species had evolved a mechanism for opening the host cuticle in order to incorporate blood of its host using these sucking organs. This is unlike the common use of homologous suckers in related mite taxa, where they (as far as known so far) only support the adherence.

Another interesting example of a phoretic mite is Histiostoma blomquisti (Histiostomatidae, Astigmata), which is specifically associated with the red imported fire ant (sometimes referred as RIFA) Solenopsis invicta, which worldwide appears as troublesome neozoon, again a result of human global traffic. I am the scientific describer of that mite, and my research about it’s biology and abundance in ant nests refers to populations in Louisiana (USA). An interesting aspect is that the ant is originally native to Southern America. We lack studies, whether the mite appears in the native habitats of the ant also as its specific cohabitant or whether it originally deals with a wider range of phoretic hosts. We do not even know, whether the mite is at all native to the same area, in which S. invicta had its natural distribution. On one hand, we hypothesise that, but there is also a theoretical option that the mite performed a subsequent host change in areas, for example in the Southern USA, where the ant was accidentally established via sandy ballast substrate of ships as neozoon. It is further more not known, whether the mite – ant – relationship is indeed neutral, at least with no noticeable harming features. I discovered (S. Wirth & J. C. Moser, Acarologia 2010) that mite deutonymphs (= phoretic instar) can attach to active nest queens in such extraordinary high numbers (hundreds of mite specimens) that mobility restrictions for the concerned queens were sometimes visible. On the other hand, my video documentations showed that even completely overcrowded queens could still freely move and, much more important: stayed reproductive. The purpose of the mites inside the fire ant nests is unknown. But generally, mites of the Histiostomatidae can appear as beneficial animals in ant nests. At least according to my findings about the mite Histiostoma bakeri, which is a phoretic associate of the leafcutter ant Atta texana in Southern USA. I discovered these mites improving the hygienic conditions inside specific nest chambers (detritus chambers) due to their fungi and bacteria feeding activities (Wirth & Moser, European Association of Acarologists proceedings, 2008).

I will in different chapters of this article repeatedly refer to examples with phoretic mites of the family Histiostomatidae (Astigmata, Acariformes). As mutualism and parasitism follow similar organism-host association patterns, I will in those chapters not each time mention again that examples with these mites do not concern parasitism, but mutualism. It is by the way no accident that both life-strategies share common features, as there are examples known, which indicate that one strategy can evolve out of the other.

Mite Histiostoma blomquisti Wirth & Moser, 2010 (Histiostomatidae, Astigmata, Acariformes) on queens of ant Solenopsis invicta, Pineville/ Louisiana, copyrights Stefan F. Wirth

Mutualism often used as neutral term for organism associations with unknown effect of both partners to each other.

The copepod (Crustacea) Ommatokoita elongata on Greenland and sleeper sharks

So called mutualistic associations can sometimes represent interactions of unknown benefits or damage regarding both of the associated partners. Another interesting example of such an association with a not yet understood status is the copepod Ommatokoita elongata (Crustacea), which was discovered as specific cohabitant on the Greenland shark (Somniosus microcephalus) and the pacific sleeper shark (Somniosus pacificus). Larvae of the crustacean in their copepodit stadium and adult females attach to the ocular globes of the shark, where they can cause visible tissue damages. They are thus considered being parasites, although alternating hypotheses assume a more neutral mutualistic copepod – shark – association, based on the sometimes high abundance of the crustacean on one shark specimen (B. Berland, Nature, 1961). There are even assumptions about a benefit contributed by the copepode to the sharks: reasearchers say that it might improve the shark’s hunting success by attracting suitable prey with bioluminescence signals.

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Shark Somniosus pacificus, Wikipedia: National Oceanic and Atmospheric Administration / Public domain

Greenland shark with copepod Ommatokoita elongata, hardly visible, when the shark turns to show his right eye, Youtube: copyrights The Canadian Press, video by Ben Singer, footage Brynn Devine, Marine institute of Memorial University of Newfoundland

Human parasites with mutualistic features: the mites Demodex folliculorum and D. brevis

Can viruses be compared with some mites, nematodes or copepodes by performing mutualistic virus – host – relationships? A priori it must be stated that they are unable for a neutral relationship with another organism, as they need the destruction of living cells for their own persistence. But indeed there are viruses known, causing no known diseases and thus being named passenger viruses. But first, an example of an organismic example of parasitism without harmfulness will be presented: the mites Demodex folliculorum and Demodex brevis (Trombidiformes, Prostigmata), which appear as so named „face mites“ inside hair follicles of humans, preferring eyebrows and eyelashes, but also other hairy body parts. The abundance in humans is high and grows with a human age. According to Schaller, M. (2004), new born children are free of Demodex, while over 70 years old people are at almost 100 percent infested with the mites. The mite in fact is a parasite and feeds on sebum from the sebaceous glands. Incorporating needed human gland secretions must be named parasitism. Nevertheless mites under normal conditions cause no visible damages nor do they seem to harm their host noticeably.

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Mite Demodex folliculorum, Wikipedia: Information |Description=Demodex folliculorum |Source|Date=2009-09-08 08:34 (UTC) |Author=: http://www.legart.ru/demodex

So called passenger viruses as mutualists with a more or less neutral affect to their human hosts

Such a parasitic relationship might be comparable with so called passenger viruses, which do not harm noticeably, although they destroy living tissue as all viruses do. They can accompany more harmful viruses and even might harm the pathological success of the diseases, caused by these harmful viruses, and for example might slow the disease’s progression. An example is the GB virus C (GBV-C), which was before known as Hepatitis G virus. The virus is common in humans and shows no pathogenic damaging effect. According to an US-study, about 13 percent of probands, whose blood was examined, possessed antibodies against the virus. GBV-C is considered to slow the effects of an HIV disease by negatively effecting the replication of the HI-virus.

Host increase towards systematically not closer related new hosts

Example for a transfer within related host taxa in mites is the bark-beetle-clade within Histiostomatidae (Astigmata), an example for non related side hosts is the mite Histiostoma maritimum (Histiostomatidae, Astigmata)

Do side-hosts or intermediate hosts as results of host increases commonly need to be systematically close relatives of the main host? The answer is no, although parasites are usually better pre-adapted in infesting a host, which shares a maximum of common characters with the main host. Within the mite family Histiostomatidae, there exists a clade of mites being associated with a clade of beetles. I named it bark beetle-clade (e.g. Wirth, phd thesis, 2004). Mites and bark beetles performed a parallel evolution, which required host increases and host changes towards related hosts and subsequent evolutionary adaptations to harmonize with these new hosts, either to become specific for a new host or to deal with a range of host species.

But the transfer of a parasite to new hosts can also happen towards not closely related host species, representing a scenery being based on a common ecological context between main hosts and side hosts. The phoretic mite Histiostoma maritimum for example is host specific for at least two closely related beetle-species of genus Heterocerus (Heteroceridae). But the mite regularly also appears on predatory beetles of genera Elaphrus and Bembidion (Elaphrus cupreus and Bembidion dentellum, Carabidae) (S. Wirth, phd thesis 2004 and subsequent studies). These beetles partly share the same habitats with Heterocerus: sapropel around ponds, being exposed to sunlight and warmth. In my research about the mite H. maritimum, I hypothesised that the phoretic mite instar might switch over to Elaphrus and Bembidion, for example when these predators feed on adult Heterocerus beetles, larvae or cadavers. Although I could regularly find mites in lower abundances over years on the side hosts (collected in the Heterocerus sampling sites), it is unknown, whether the „switch-over“-scenario was a starting event in an evolutionary past to establish the mite to new additional hosts, where they would today survive more or less independently from the original Heterocerus source, or whether the mites regularly need to switch over in the above mentioned situations, and in consequence side hosts with no Heterocerus-contact would thus lack the mite. A possible support for the latter hypothesis are my laboratory findings about the preferred developmental habitat of the mite, which was cadavers of died Heterocerus beetles. In my experiments the mite remained on its Heterocerus– carrier until this died. Mites subsequently developed on the beetle’s cadavers, feeding there on bacteria and fungi (the phenomenon is named necromeny). Mites under laboratory conditions developed also seemingly successfully on E. cupreus– and B. dentellum-cadavers. But I could so far never continue these studies and don’t know, whether or how well mite colonies with having only cadavers of these two side-hosts available would reproduce compared to mites being reared in Heterocerus settings. In case of a strict substrate specialization for Heterocerus cadavers, the side hosts would be dead-end hosts, and permanent reinfections from the original host source would be required to explain the regular mite abundance in Elaphrus and Bembidion.

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Histiostoma maritimum, a adult female with conspicuous copulation opening, b both adult genders in dorsal view, c, d copulation opening in dorsal and sideview, SEM, Berlin 2020/ ca. 2002, copyrights Stefan F. Wirth

Assumed transfer of virus SARS-CoV-2 from bat main hosts via a pangolin as intermediate host towards humans:

There is an ecological context between bats and pangolins

The new corona virus SARS-CoV-2 is assumed to be host specific to a group of animals and from there infesting another animal as intermediatehost, from which presumably humans were opened up as new host source. There are researchers interpreting us humans as an dead-end hosts, as unlike in bats human people can be harmed remarkably with the lung disease COVID-19 (corona virus disease 2019), triggered by SARS-CoV-2. As at least from a general statistical point of view a high majority of infested people shows no or only slight symptoms, thus it can up-to-date not be excluded that Homo sapiens is in order to become a fully potential side host, because all a parasite needs in order to „survive“ before all other requirements is the (statistically) surviving of its host.

There is evidence that bats (Chiroptera) represent the main host, thus representing the „natural virus reservoir“, while pangolins (Pholidota) presumably act as intermediate hosts. This main-host-to-intermediate host context is for example reported as putative scenario by Ye Z.-W et al. (Int Biol Sci, 2020), who stated that based on molecular features the bat Rhinolophus affinis (Rhinolophidae, Chiroptera) is hosting a virus most similar to SARS-CoV-2 differing from all other known corona viruses (Similarity 96.2 %, nucleotide homology). The pangolin species Manis javanica was identified to carry formerly unknown CoV genomes, being according to the same authors with 85-92 % similar to SARS-CoV-2 (nucleotide sequence homology).

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Megabat Cynopterus brachyotis as example for a species native to Southeast Asia, Wikipedia: Anton 17 / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

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Bat Rhinolophus affinis as known reservoir of a virus most similar to Sars-CoV-2. Wiki commons: Naturalis Biodiversity Center

Pangolins and Chiroptera (bats and megabats, this taxon subsequently sometimes refereed as „bats“) are systematically not closer related to each other. Pangolins (Pholidota) are considered to represent the sister taxon of the clade Carnivora. Chiroptera were reconstructed as sister taxon to the clade Euungulata (containing animals such as horses, cattle or whales). But both, Chiroptera and Pholidota, can be connected by an ecological context. Pangolins (Pholidota) are species, which are either adapted to live preferably on the ground, or to spent most of their time on trees. Both types are specialised ant and termite feeders, which use cavities on the ground or inside trees as hideaways. They additionally give birth to their offspring inside these burrows and subsequently use to stay there with their young for a while. Such cavities can accidentally be the same time aggregation and resting places for bats, excluding megabats, which use to rest during daytime on exposed areas on trees. Manis javanica has a semi-arboricol life-style, spending time in trees and on the ground. This pangolin uses different resting cavities, either subterranean burrows or tree cavities.

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Chinese pangolin Manis pentadactyla, a ground living species, Wikipedia: nachbarnebenan / Public domain, Zoo Leipzig, Tou Feng

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Pangolin Manis javanica as known host of a virus similar to virus SARS -CoV-2. Wikipedia: creative commons Piekfrosch / CC BY-SA

Chiroptera and Pangolins are in South Eastern counties often subject to hunting, as both for example play a role in the traditional Chinese medicine. Thus a virus transfer to humans via main host or via the putative intermediate host is assumed to have happened on animal markets (in the province Wuhan in China).

Which indications point to animal hosts as original source of virus SARS -CoV-2 ?

The scientists Andersen et. al (2020) explain there was no virus-engineering instead of a natural evolution

But which proofs exist that animal hosts sources such as Chiroptera and pangolins are involved in the transfer of the virus SARS -CoV-2 to humans? The lack of general knowledge is still fundament for conspiracy theories, such as an artificial creation of the new corona virus in laboratories with biological warfare purposes.

K.G. Andersen et al. („The proximal origin of SARS-CoV-2“, Nature Medicine, 2020) concluded based on their molecular research that the genetic template for specific spike proteins forming structures, which the virus body possesses on its outside for holding on and penetrating into the host cells, showed evidence for a natural evolution and not for an engineering. They argue with the strong efficiency of the spikes at binding human cells, which makes an engineering implausible and evolution based on natural selection highly probable. The authors additionally examined the overall molecular structure of the backbone of SARS-CoV-2. Backbone can be explained as the „skeleton spine“ of a macromolecule as a continuous row of covalent bond atoms. This overall backbone structure of the new corona virus is according to the authors similar to viruses, which were isolated from Chiroptera and pangolins and dissimilar to other corona viruses, which are already known to science.

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Spikes (here in red) in Sars-CoV-2 hold on and penetrate into host cells, Wikipedia: CDC/ Alissa Eckert, MS; Dan Higgins, MAM / Public domain

Can a host increase happen more or less spontaneously with a subsequent enormous success (as for example in virus SARS-CoV-2)?

And: Can the complexity of adaptations to a main host decide for the option of a host increase?

An example for a tendency to spontaneous temporary host changes is mite Histiostoma piceae (Histiostomatidae, Astigmata)

Is it imaginable that a host change or a host increase happens spontaneously and subsequently having such a remarkable impact to the new host, as it is recently ongoing with the SARS-CoV-2 pandemic? Host specificity, host changes and parasitism or mutualism in general are result of evolution. The most common case of evolutionary changes in organisms or viruses is a slow process of stepwise modifications being based on mutations and natural selection.

But it needs also to be stated that as more complex the pattern of characters is (genome, morphology, behavior, function-morphology, reproduction biology etc.), which binds a parasite or mutualist to a specific host, as more evolutionary steps are necessary to perform a host change and as longer an exposure to mutation and selection would need to take place. However it is alternatively possible that a host specificity is only based on a few, but important features. Slighter ecological pressures focusing towards these features might then theoretically allow rather fast host changes.

As an example with a putatively reduced complexity of host adaptations I herewith introduce the phoretic mite Histiostoms piceae (Astigmata, Histiostomatidae), which I repeatedly studied and reared under laboratory conditions. The scientific describer of this species (Scheucher, 1957) discovered a strict host specificity to the bark beetle Ips typographus. According to my and her research, the mite has along the geographic distribution of that bark beetle a high abundance, beetles without the mite are rare. In 2016 I discovered H. piceae being additionally associated with Ips cembrae as a second regular host. I cembrae represents the sibling species of I. typographus (Wirth, Weis, Pernek, Sumarski List, 2016). Exceptions are smaller bark beetle species, which regularly burrow their galleries into those of I. typographus or I. cembrae. It is unknown, whether these small bark beetles as cohabitants of I. typographus carry the mite temporarily or regularly. But the former might be confirmed by the following interesting phenomenon in the mite H. piceae:

In case of very high numbers of mites inside bark beetle galleries and a relatively low numbers of corresponding Ips species, the phoretic instar of the mite attaches under natural field conditions all available arthropods inside or adjacent to the galleries of the main hosts, including bigger mite species, different beetle species or – as already mentioned – smaller bark beetle species (for example my studies in the area of the city Tyumen, Siberia, Russia, 2015-2016). This indiscriminateness for specific hosts under certain conditions might indicate that the substrate specificity of the mite H. piceae is more developed than the phoretic specificity for the host insect itself as a carrier . In such a case, I would generally expect that a host change or a host increase might faster happen in future evolutionary steps than in mite species, which are strictly choosy for their specific host carrier. In H. piceae the tolerance for a variety of carriers (unlike the specificity for substrate conditions) might in a future evolution even succeed as pre-adaptation, which under suitable circumstances might spontaneously allow a regular transfer to new hosts. A second important step towards a real host increase would require that the mite becomes able to stay permanently on its new host. In the H. piceae context the evolution of a tolerance for different substrate conditions might once become an important selective factor in may be opening up new permanent host-associations.

Temporary side hosts, as described in the above explained observations, would represent nothing then dead-end hosts, as they are unable to carry the phoretic mite to suitable habitats for its development. But under favorable circumstances, a former dead-end host might even become a new permanent host.

Histiostoma piceae, a adult female in side view, b in dorsal view, c mouthparts and digitis fixus, d adult male in dorsal view, e in ventral view, Berlin 2020/ ca. 2002, copyrights Stefan F. Wirth

hpiceaeimage0498photoshop

Phoretic instar of Histiostoma piceae, ventral view, lightmicroscope with dig contrast, Tyumen (Siberia, Russia), 2016, copyrights Stefan F. Wirth

Two possible ways of virus transfer from bats to humans according to Andersen et al. (Nature Medicine, 2020)

Did the virus evolution towards the recent state happened prior to a first human infection, namely inside animal main host populations, or did it happen afterwards inside human populations?

As there is not yet much known about the presumed host specificity of the virus SARS-CoV-2, Andersen et al. (Nature Medicine, 2020) reconstructed based on their up-to-date knowledge two possible ways of a virus transfer from bats to humans and finally to the recent pandemic situation in the world:

The virus might have evolved its recent human-pathogenic features within the main host populations of bats. Natural selection must have been the corresponding major driving force. The relevant adaptations are represented by the above mentioned two molecular characters of the spike proteins in SARS-CoV-2 (receptor-binding domain for host cell binding and cleavage sites for an opening up of the virus). Under such circumstances the authors expect that the infection of humans could have happened with an immediate effect, leading at once into the pandemic situation of today. An intermediate host would in this option be not obligatory. A direct transfer from bats to humans might be imaginable.

The second option is based on findings that corona viruses in pangolins possess similar receptor-binding domains (RBD) as in the human SARS-CoV-2 version. Thus the authors reconstruct a version according to which a non or less pathogenic form of the new corona virus was via pangolins transferred to humans and circulated there for an unknown period of time. Even further possible intermediate hosts, such as ferrets or civets, are considered to have been involved in that scenario. During its time inside human populations the virus would have developed its recent features due to evolution and finally was able to be spread explosively between human populations on a pandemic level.

A higher probability for one of the two scenarios can according to the up-to-date knowledge not be assumed

I am not sure, whether the authors take under consideration with their second option that pangolins might even represent a main host and whether bats would not necessarily be involved in the animal-human transfer of the virus. But according to Ye Z.-W. et al. (Int Biol Sci, 2020) the context between bats, pangolins and humans was stated: „We cannot exclude the possibility that pangolin is one of the intermediate animal hosts of SARS-CoV-2“. But whether the pangolin is intermediate host or main host would at this point not effect the general conclusion of each of the two scenarios. The virus was either pre-adapted regarding efficient spike protein characters and then infested human populations rapidly or was transferred to humans via an animal host and subsequently evolved its key-features for a pandemic „success“ within human populations. Although the authors have up-to-date no indications allowing a preference for one of the scenarios, they point out that the potential of new SARS-CoV-2 outbreaks after the extinction of the recent human pandemic would be much higher in case of the scenario one, as the pathogenic virus would under these conditions survive in the animal main host populations.

I would as addition to scenario two suggest to test a modified hypothetic scenario, in which the non pathogenic ancestral version of the virus did not only circulate between human populations until it reached its pandemic key-features, but even circulated between humans and animal hosts forth and back for a longer time. This would according to my understanding of evolution improve the probability of a stepwise evolution of important key-features.

Special and unusual features of main hosts can improve the diversity within their parasites, important conditions for subsequent host changes: a very efficient immune system in bats pushes the evolution of their viruses

Chiroptera (bats and megabats) are not only known as putative main hosts for SARS-CoV-2, but also for Mers, Sars, Marburg and ebola viruses. Scientists did a research about the question, whether there are specific features existing, which explain, why Chiroptera are favorable hosts for viruses with a seemingly potential for epidemic and pandemic effects in human populations.

C. E. Brook et al. (eLife, 2020) discovered an unusual efficient immune system in Chiroptera, which they think protects these hosts from harmful diseases by their virus parasites. This bat immune system is considered being the evolutionary driving force for the variety of viruses and their relatively fast modifications, as they would need to compete with immune system responses by regularly evolving new adaptive features.

The authors discovered that the antiviral messenger substance interferone-alpha is released in most mammals as a response to the detection of viral genetic material inside body cells. Whereas they found Chiroptera releasing this messenger substance permanently. This would according to the scientists enhance the virus defense in bats and might explain that the above named viruses do not trigger noticeable diseases in their main host recervoir.

I would resume that such conditions might support the scenario one of Andersen et al. (Nature Medicine, 2020), according to which viral key features to infest humans had evolved prior inside the animal host populations. Regular new virus modifications as result of the competition between these viruses and their bat-host immune responses might support the randomness of the development of features, which as pre-adaptations could support a relatively fast host change. Even when I generally prefer scenarios of stepwise adaptations of organisms to new conditions, a higher probability of the availability of suitable pre-adaptations might at least accelerate evolutionary proceedings.

Longtime parasite – host – relationships, a dead-end for the parasite?

Are relationships between organisms over longer time periods of advantage or disadvantage for parasitic or mutualistic passengers? A longtime host specificity of a parasite (or mutualist) requires a strict specialisation, which means complex morphological, ecological and behavioral adaptations.

According to the acarologists P. B. Klimov & B. Oconnor (Systematic Biology, 2013) long-term specialisations could impede the flexibility of such organisms to react to environmental changes via evolutionary adjustments. Thus parasites with long-term relationships to the same hosts might be endangered to reach a dead-end. They would die out. A possible way out from such a disastrous end can be a re-evolution of the parasite back to its ancestral free living conditions, a situation prior to the evolution of its parasitic host specificity. But Dollo’s law states that a complex trait cannot re-evolve again. Thus long-term parasitism could according to the law not other than leading into a dead end. Nevertheless the authors could present an impressive example as proof to the contrary: based on their complex research about house dust mites, the acarologists reconstructed that these mites were originally parasites of warm blooded animals and subsequently evolved into free living associates of mammals, as which they are of medical relevance due to the remarkable allergic reactions in humans.

I think that the access of this paper does contain enough general biological aspects to ask, whether the dead-end scenario of long-term parasite relationships might also concern viruses, which don’t have an option for a free living existence, as they don’t live at all and are unable to perform independent strategies. At least might this long-term scenario support the findings of C. E. Brook et al. (eLife, 2020) that only unusual and regularly changing features of a long-term host might trigger regular corresponding responses by the parasite, another option to prevent a parasite from a dead-end due to a long-term host relation. This might explain, why certain viruses often parasite bats and successfully persist there, while other suitable hosts lack the very efficient immune system of bats and thus cannot host a specialized virus permanently. Regarding SARS-CoV-2 such theories might indicate that the virus would finally move towards dead-ends in humans and other host species, but might permanently survive in chiropterans. It’s a statement only being worth of consideration, in case of scenario one of Andersen et al. (Nature Medicine, 2020). And only in case, it would come out that the virus adapts well to humans, which would require a much reduced harmfulness, as parasites cannot survive by killing their hosts. In case of a dead-end host due to high mortality rates instead of a normal host increase, aspects of a long-term relationship with such a host don’t need to be discussed, as a shorter temporary outbreak and no beginning of a long-term relationship at all would result out of it. One needs additionally to consider that viruses as non living organic bodies with genome and with an unusual ability for fast modifications might often not fit into biological models based on living organisms.

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House dust mite Dermatophagoides pteronyssinus. Wikipedia creative commons: Gilles San Martin from Namur, Belgium / CC BY-SA

Summary

Host specificity must be differed from generalism. Known host-parasite specializations include a complexity of strategies. And even different kinds of hosts must be named, such as main host, side-host, intermediate host or dead-end host. Evolutionary steps such as host increase, host change or temporary hosts can appear. Parasitism and mutualism differ from each other as life-strategies, but share common features as association between different organisms: host specificity follows similar rules, an indication that both life-modes can evolve out of each other. The human globalization sometimes supports the spreading of parasites or their hosts over the world, host changes or host increases can thus be performed including organisms, which would under normal conditions get no contact to each other.

Viruses do not represent living organisms, but protein lumps with a genome and depend on living host cells for their reproduction and „survival“. like in living organisms, also viruses underlay the mechanisms of natural selection and evolution. Viral parasite – host – relationships show general similarities with features in living organisms, including options for a host change or host increase, the use of intermediate hosts or a kind of mutualism (passenger viruses).
There is evidence that the main host reservoir of SARS-CoV-2 are Chiroptera, while pangolins (and other mammals) might represent intermediate hosts. Humans are either dead-end hosts (preferred by most authors) or result of a successful host increase. Researchers could not yet decide, whether features to infest humans in a pandemic context evolved prior to the transfer to humans inside animal main host populations or whether a harmless version changed to humans and in their populations evolved its pandemic potential. A major drive motor for a long-term successful relationship with bats is the unusual immune system in chiropterans.

Copyrights Dr. Stefan F. Wirth (phd), all rights reserved, excluding photos labeled as creative common content from Wikipedia sources. Berlin, 2 April 2020

References:

J. R. H. Andrew’s (1983): the origin and evolution of host associations of Sarcoptes scabiei and the subfamily Sarcoptinae Murray. Acarologia XXIV, fasc. 1.

B. Berland (1961): Copepod Ommatokoita elongata (Grant) in the eyes of the Greenland Shark – a possible cause of mutual dependence. In: Nature, 191, S. 829–830.
Cara E. Brook, M. Boots, K. Chandran, A. P. Dobson, C. Drosten, A. L. Graham, B. T. Grenfell, M. A. Müller, M. Ng, L-F. Wang, A. v. Leeuwen (2020): Accelerated viral dynamics in bat cell lines, with implications for zoonotic ermergence, eLife; 9:e48401.g W

Pavel B. Klimov, Barry OConnor, Is Permanent Parasitism Reversible? (2013): —Critical Evidence from Early Evolution of House Dust Mites, Systematic Biology, Volume 62, Issue 3, Pages 411–423.

Kristian G. Andersen, Andrew Rambaut, W. Ian Lipkin, Edward C. Holmes, Robert F. Garry (2020): The proximal origin of SARS-CoV-2. Nature Medicine.
Martin Schaller: Demodex-Follikulitis. In: Gerd Plewig, Peter Kaudewitz, Christian A. Sander (Hrsg.): Fortschritte der praktischen Dermatologie und Venerologie 2004. Vorträge und Dia-Klinik der 19. Fortbildungswoche 2004. Fortbildungswoche für Praktische Dermatologie und Venerologie e.V. c/o Klinik und Poliklinik für Dermatologie und Allergologie LMU München in Verbindung mit dem Berufsverband der Deutschen Dermatologen e.V. (= Fortschritte der praktischen Dermatologie und Venerologie. 19). Springer Berlin, Berlin 2005, ISBN 3-540-21055-5, S. 273–276.

Wirth S. (2004): Phylogeny, biology and character transformations of the Histiostomatidae (Acari, Astigmata). phd thesis. Internet Publikation FU Berlin, http://www.diss.fu-berlin.de/2004/312.

Wirth, S. & Moser, J.C. (2008): Interactions of histiostomatid mites (Astigmata) and leafcutting ants. In: M. Bertrand, S. Kreiter, K.D. McCoy, A. Migeon, M. Navajas, M.-S. Tixier, L. Vial (Eds.), Integrative Acarology. Proceedings of the 6th Congress of the European Association of Acarologists: 378-384; EURAAC 2008, Montpellier, France.

Wirth S. & Moser J. C. (2010): Histiostoma blomquisti N. SP. (Acari: Histiostomatidae) A phoretic mite of the Red Imported Fire Ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Acarologia 50(3): 357-371.

Ye ZW, Yuan S, Yuen KS, Fung SY, Chan CP, Jin DY (2020): Zoonotic origins of human coronaviruses. Int J Biol Sci ; 16(10):1686-1697. doi:10.7150/ijbs.45472.

Zhang W., Chaloner K, Tillmann HL, Williams CF, Stapleton JT (2006): „Effect of Early and Late GB Virus C Viraemia on Survival of HIV-infected Individuals: A Meta-analysis“. HIV Med. 7 (3): 173–180.

https://www.sciencedaily.com/releases/2020/03/200317175442.htm

Oribatida mites: Fast runners and slow crawlers

Microhabitats often consist of a complexity of organism species. Under suitable conditions, samples can be kept „alive“ for months and even for years by regularly adding moisture and organic tissue, in case of my sample of this footage: patato pieces.

 

 

Mites of the Oribatida and their different ways of locomotion. Copyrights: Stefan F. Wirth, Berlin April 2019. Please give the video a like on youtube too.

 

Soil samples from island Norderney

 

This soil sample was collected in summer 2018 on the North Sea island Usedom during my participation at the „Geo Tag der Natur“. It contained several specimens of the predatory chilopode Lithobius sp. and pieces of rotting wood, moss and forestground, everything collected under rotting treetrunks and tree branches. The samples additionally contained the carabid beetle Pterosticus cf. niger and ants of genus Lasius. Samples were collected in a small forest area with wetland aspects. The soil quality was rather moist.

 

Astigmatid mites

 

I later added potato pieces and regularly some water droplets to the sample with still living big arthropods/ insects. After some weeks, specimens of the astigmatid mite Acodyledon cf. schmitzi developed on dryer areas of the potato pieces. These mites were presumably phoretic associates of the carabid beetles. They died out after several months, after the sample had dried out a little bit and may be due to changes of the room temperature during winter time.

 

Oribatida

 

Now, almost a year later, the micro habitat is inhabited by mites of the Oribatida in greater numbers of specimens of at least three species: Nothrus sp. (genus not yet clarified), Nothrus palustris (already found for the first time shortly after the sample collection) and a species of Phthiracarida.

 

Locomotion and biodiversity

 

Purpose of the short film is to show different organisms, cultured after about a year in this sample: mites, nematodes, collembolans and microorganisms, fungae and bacteria. Of the bigger arthropods/insects, only one Lithobius species survived until now.  Also the diversity of ways of locomotion in different oribatid species is emphasized: There are slow crawlers (Nothrus) and fast runners (Phthiracarida).

 

Berlin, April 2019, Copyrights Stefan F. Wirth

Mite Histiostoma sachsi (Astigmata): Juvenile dispersal instar deutonymph and its orientation behavior

Some animals live in environments, where there is (almost) no light available. It makes no sense to see in the dark, but it is important for a specimen to know, where it actually is, where it is going to, whether there is enough food and what the conspecifics are doing. Predators need to be recognized in time, and a sexual partner must be found. There is also need for an efficient communication between specimens of a species. How can all this be performed by mites of the Astigmata, which usually live inside decomposing soil habitats in a more or less permanent darkness?

 

Olfactory sense organs in mites of the Histiostomatidae

 

Histiostoma sachsi (Histiostomatidae, Astigmata) is such a mite, living inside cow dung or compost. It might have a rudimentary ability for a light perception, but has not visible or functional eyes. It cannot produce any sounds. It can only feel and smell. Seemingly very limited abilities, but the contrary is fact: Due to evolution this mite is perfectly adapted to its life-style. It can feel objects by touching on them using its body setation (= body hairs). And it smells by means of very specialized body hairs, which are called solenidia and appear in different types, shapes and functions. These mites don’t smell on the level of us humans, which would be very insufficient. If at all, it should be compared with a dog. I am always fascinated when seeing blind dogs and how perfectly they can interact with their environment, despite their handicap. That’s may be how the efficiency of olfactory perception abilities of such a mite must be imagined. They do not only perceive scent particles from other animals, plants and soil components. Even olfactory signals from their conspecifics will be correctly and differentiatedly interpreted. And that not only marginally.  Olfactory signals represent indeed the major mode of their intraspecific communication.

 

Chemical communication of mites of the Histiostomatidae

 

Communication always requires contributions from both sides, a signal and an answer. These mites smell the signal of a conspecific using their solenidia, and they answer by the secretion of biochemical components. For these purposes, they possess a huge and complex gland system located on the upperside of their backs. Volatile excretions aggregate inside a big and rounded reservoir and finally leak to the outside via a pore, called oilgland opening. These gland systems are located symmetrically on both sides, each with one reservoir and one pore.

The meaning of the sent volatile message simply depends on the composition of the correspondingbiochemical components. Even diffferent stereochemical configurations of the same molecule can have different meanings. Citral for instance is a major component and has in different stereoisomers different functions. Such cummunicative volatile signals are usually named pheromones. And mites of the Histiostomatidae can indeed produce different kinds of pheromnes via the same gland system. Aggregation pheromones inform specimens about a suitable place to stay together with their conspecifics, for example due to a sufficient amount of food resources. Alarm pheromones solicit mites nearby to flee from an unpleasant situation. Sexual pheromones attract adult partners to each other in order to perform the mating procedure. But the gland secretions can even more. As allomones, they communicate with specimens of other species. They function as defenses against predators or other dangerous cohabitants.

 

Deutonymphs need to find a carrier for dispersal

 

Another form of communicative interspecific interactions is performed by a specific juvenile instar, the deutonymph. It looks morphologically quite different from all other instars (heteromorphic situation), does not need or possess a functional mouth, has a thicker cuticle as protection against drying out and a complex sucker organ on its underside in order to attach itself to an insect or another bigger arthropod. Deutonymphs of the astigmatid mites search for bigger carrier-arthropods to get carried from one habitat to another (dispersal strategy  is calledphoresy). While doing so, they again use their specifically modified leg setation (hairs) on the first pairs of legs to perceive scents for the detection of a suitable and passing by carrier. Basically it is still unknown, whether the term „communication“ is indeed appropriate in this context as we don’t know yet about a mutual interaction between deutonymphs and their carriers, before the phoretic ride begins.

 

 

Olfactory orientation of the deutonymph of Histiostoma sachsi, copyrights Stefan F. Wirth, February 2019.

 

Specific way of walking in deutonymphs

 

In detail, different kinds of behaviors can be observed in deutonymphs, when searching a carrier. The detailed behavioral patterns in this context can slightly differ between even closer related species. Deutonymphs of Histiostoma sachsi as all deutonymphs show a characteristic mode of walking, in which especially the first pair of legs plays an important role. During each step, performed by four pairs of legs, the first legs are lifted up much higher than all other hind legs. While doing so, they slightly tremble up and down. A behavior that mostly supports a better basic orientation inside a „jungle-„micro-landscape, being filled up with soil particles and decomposing plant tissues. But what H. sachsi deutonymphs additionally need in order to find their carriers is repeatedly to rest between the walking activities. Thus the first legs, which normally are still walking legs, are made free and that way available for the perception of carrier-scent-components only. These  namely are the legs that bear the highest densiy of solenidia.

 

Two different behavioral modes for an efficient orientation towards a carrier

 

Two different modes of resting with olfactory searching activities could be observed: In periodic intervals the deutonymph attached to the ground by using its sucking structures. They were then more or less laying on their entire undersides with only their forebodies slightly lifted up. By alternating moving the first legs up and down, olfactory information could be perceived from all directions without having the own body as a barrier to backwards. To improve its orientation situation, the deutonymph additionally turned on its own axis around, being stabilized by its sucking structures, which are flexible enough to follow these movements. When the deutonymph intended to continue its walk, it first needed to detach from the ground, which happened via muscle contractions that caused an abrupt detachment of the corresponding suckers. But main aim of the deutonymph is to find an elevated place, where the probability of a passing by carrier is especially high and from where a bigger insect (or other arthropod) can easier be ascended. There the second behavioral mode was performed. The deutonymph only fixed the edge of its hind body to the ground, again using the suckers on its underside, which are located close to this edge. This time the entire mite body stood in an upright position. The first legs again „waved“ alternating up and down and could under these especially elevated conditions even perceive scents from bigger distances. By occasionally slightly and alternating turning their upright bodies to both sides, olfactory information could be easier detected from all directions.

 

Carrier of H. sachsi still unknown

 

The frequency of such movements in mites increases typically as closer a suitable carrier approaches. But this was not yet observed or documented for Histiostoma sachsi. Its carrier inside the compost substrate is still unknown, which is why I so far could’t perform corresponding experiments. The species‘ describer, Scheucher (1957), found her mite specimens in cow dung and also didn’t identify the corresponding carriers there.

The observations presented in my video are part of my research project about morphologies and behaviors of deutonymphs in the Histiostomatidae.

 

Berlin, February 2019. All copyrights Stefan F. Wirth.

 

Eudicella colmanti – Mating behavior of a colorful beetle

Rose chafers represent a group of colorful beetles, which taxonomically belong to the Scarabaeidae and thus are relatives of famous beetles such as Scarabaeus sacer, well known for rolling dung into balls and for being an important symbol for creation and the rising sun in the ancient Egyptian world. Even the stag beetles are more distant relatives of rose chafers.

 

Colorful and active during daytime

 

Unlike some related beetle clades, rose chafers are usually active during the day. This is also indicated by their very colorful bodies. Colors in insects can have different functions, but they usually all are optical signals, which require a visibility in the sun light. Greenish colors are common in rose chafer species and might have optical inner specific signal functions, but also might support an optical camouflage. This would also make sense in the preferred habitats of the adult beetles, which usually feed on softer parts of blossoms and on their pollen. But they also feed on fruits, whereby mostly liquids are incorporated as the chewing mouthparts are not very well developed.

 

Tropical rose chafer Eudicella colmanti during its copulation behavior, 4K videography, copyrights Stefan F. Wirth.

 

Tropical rose chafers from African countries

 

About 3000 species of rose chafers are known, of which most inhabit the tropical zones. The about 20 species of the genus Eudicella are more or less restricted to the African continent.

Eudicella colmanti is native to Gabun, Kamerun and Kongo, thus a species with a main distribution in Central Africa. But E. colmanti is like other species of this genus worldwide often kept in terraria, although species like E. smithi are more common inhabitants of this kind of artificial habitats. They all can be more or less easily reared.

 

Specific flying mode and copulation behavior

 

This is why I was able to study behavioral characters in detail. And rose chafers indeed show interesting behaviors. They for example perform a unique way of flying. It is a specific character of rose chafers (a so called apomorphy) that they fly with closed fore wings, which cannot be opened as in other beetles.

I documented in my video the mating behavior of a beetle couple. Interestingly this was not too difficult, although both genders can, when separated from each other, react to disturbances with a high agility.

 

Almost permanent copulation activities

 

But in the copulatory position, they accepted to be removed from their terrarium to the filming set and even stayed in position, when they were enlighted from different positions with very bright light beams. Please note the the female, which I observed regularly actively searching for a position underneath the male (behavior not clearly visible in my footage). But it also conspicuously never stopped feeding (on an apple) during the copulatory process (very well visible in my footage), obviously to obtain enough nutrients for the production of eggs. A copulation in my couple is not a unique event, but is repeated regularly and can take hours.

 

Phoretic mites

 

Both genders carried bigger numbers of mites. These were phoretic deutonymphs of the taxon Astigmata (Acariformes, Acaridae). As never determined the mite species, as it was not clear, whether it represented a natural associate of these tropical beetles, or whether it was a species native to Germany, which for example was carried into the terrarium via Drosophila flies.

Copyrights Stefan F. Wirth, Berlin March 2017/ February 2019

Berlin forest Grunewald – former gravelpit area, type location for the mite Histiostoma palustre

The city of Berlin geomorphologically consists of witnesses of the Weichselian glacier. The modern city itself and adjacent federal states represented end moraine areas with fluvio-glacial debris accumulations,  even well visible today due to a very sandy soil composition and a corresponding vegetation, creating landscapes, which partly almost look like from around the Mediterranean Sea.

Sands carried by the glaciers towards their end positions remained in partly huge layers with a thickness of up to 20 meters or more.

 

Gravelpit zone and its history

 

Also the area of the old gravelpit zone, called „Sandgrube im Jagen 86“, in the Berlin forest Grunewald is located inside such an end moraine zone, which was represented by plates belonging to the geological Teltow-plateau. In the time period between 1966 and 1983, gravel was excavated for industrial purposes. After 1983 a part renaturation was supported by nature conservationists. In 1992 in total 13 hectares of the former gravelpit area were allocated as nature conservation areas.

Other parts of this unique landscape remained accessible for the public. They represent today popular places for leisure and experiences of nature. Especially the huge sand dune is a popular destination for families with children.

 

Aerial videography of the gravelpit area in January 2019, copyrights Stefan F. Wirth. Please like my video also on Youtube, in case you like it.

 

 

Gravelpit zone and its ecology and biodiversity

 

The whole area – nature protection and accessible zones – show a complex mosaic of different  landscape types, offering numerous animal and plant species a well suitable refuge.  Neglected grasslands and dry meadows are surrounded by sandy areas free of any vegetation („dunes“) and moist osier beds and wetlands with ponds. The wetlands represent breeding grounds for numerous amphids. Lizards such as the sand lizard Lacerta agilis and snakes such as the grass snake Natrix natrix can regularly be observed. Sandy habitats offer space and specific ecological conditions for a interstitial fauna, consisting for example of different bee and sand wasp species.

In total the area bears more than 300 ferns and flowering plants, 16 breeding bird species, 7 amphibian species and 188 butterfly species.

 

My own scientific mite research in the gravelpit area

 

I was performing scientific research in that gravel pit landscape during the work on my phd-thesis between 2000 and 2005. My interest was (and one of my interests is still) focussed on specific organisms living around the shoreline of ponds.

The whole area of the gravelpit landscape is a good example for ecological changes that happen naturally with the ongoing time or even being affected by climatic changes. Between 2005 and 2018, the landscape partly changed significantly. Neglected grasslands and dry meadows covered less space originally, and instead several smaller ponds existed and offered amphibs and wetland inhabiting insects additional habitats. But some of the ponds already years ago dried out permanently. Their remnants are now covered by extended dry grasslands.

In former times of my phd thesis and even today, my research interests focus and focussed on the mite fauna in and around the muddy shorelines of ponds inside this former gravelpit area. The ponds are mostly surrounded by sapropel, a seemingly black and brownish mud, which is colored that way due to the incorporation metal sulfides. These muddy areas develop due to biochemical modifications of organic material in the absence of oxygen. Different insects, especially beetles live on top of these waterside habitats or even inside. Carabids of genera Elaphrus or Bembidion represent predators, while heterocerid beetles of genus Heterocerus are substrate feeders, presumanly with a preference for diatoms. Also water beetles of Dytiscidae and Hydrophilidae inhabit these habitats.

 

The mites Histiostoma maritimum and Histiostoma palustre

 

I discovered some of these beetles as dispersal carriers for specific mites. The dispersal strategy to take a ride on bigger animals to become carried from one habitat to another is called phoresy. Mites of the Astigmata represent typical phoretic organisms. I am scientifically specialized in a specific family of the Astigmata, which is named Histiostomatidae, and I discovered the mite species Histiostoma maritimum Oudemans, 1914 on Heterocerus fenestratus and H. fusculus as well as on Bembidion and Elaphrus species insside and on top of these muddy zones. I was the first acarologist, who ever studied the biology of this mite species. I furthermore discovered another mite species that was completely new to the scientific knowledge, and thus I scientifically described it as Histiostoma palustre („palustris“ = „muddy“) in 2002.

This species deserves particularly mention due to an unusual biological phenomenon: populations show a so called male dimorphism (better diphenism). Besides males with a „normal“ morphology, morphologically modified males appear. Their second legs differ from the typical shape of a mite and are modified into clasping organs. The function of these conspicuous organs could so far only be interpreted in the context of male to male competition conflicts for a female. In such situations, I observed the organs being used as arms against other males, against such ones with and such ones without clasping organs.

 

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Right modified leg of a male of Histiostoma palustre. Copyrights Stefan F. Wirth, 2002/ 2019

 

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Modified leg of a H. palustre male in closed position. Copyrights Stefan F. Wirth, Berlin 2002/ 2019

 

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Underside of a H. palustre male with modified leg. Copyrights Stefan F. Wirth 2002/ 2019

 

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Asymmetry: male of H. palustre with only the right leg modified. Copyrights Stefan F. Wirth 2002/ 2019

 

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Asymmetry: male of H. palustre with only the left leg modified. Copyrights Stefan F. Wirth 2002/ 2019

 

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Copulation of a Histiostoma palustre male with both-sided modified legs. Copyrights Stefan F. Wirth, Berlin 2002/ 2019

 

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Details of a copulation with a modified male, copyrights Stefan F. Wirth, 2002/2019

 

 

Berlin, January 2019. Copyrights Stefan F. Wirth

Phoretic Mites waiting on Ant Pupae

Greater numbers of pupae from a nest of the myrmecine ant Myrmica rudinodis are attached by phoretic mites, which wait for these pupae to hatch. They would then attach the newly developed ants to be carried around and dispersed this way. They this way had already occupied their later ants before, namely during their pupal stage, one could call this phenomen „pupa-guarding“. In my samples, I discovered two species of mites performing this pupa guarding behavior. Most abundant were deutonymphs of the mite Forcellinia wasmanni (Astigmata). But also individuals of a mite species of the Gamasina were repeatedly discovered sitting on pupae, where they were hiding between head, ventrum and limbs of the pupa. They even seemed to defend their pupae, when they felt disturbed, e.g. by my filming activities.

 

Ant pupa guarding by mitees, looking for a carrier for dispersal

 

These pupa guarding-findings concerning this ant and with these corresponding mite species might be new to science (so far I didn’t found literature indications) and thus need to be studied closer in the future in order to understand the whole context of behaviors. In the footage, two types of pupae are visible, pupae of the winged alates and those of workers. Mites generally prefered both, but especially the deutonymphs of Forcellinia wasmanni seemed to appear more often on the pupae of later workers. Most pupae had at least one deutonymph attached, rarely, there were found up to four individuals. This is different to what could be found on older workers. They on their ventral side can have 4-6 deutonymphs. Many workers seem to be covered with the deutonymphs, but I didn’t check more workers until now, so I can’t say, how many were without mites. It is unknown, how deutonymphs come to the pupae, whether they simply leave older workers for the pupa-guarding or whether they were waiting in the soil for the pupae to arrive (due to the brood caring activitoes of the ants).

Mite-Life inside an ant nest. Copyrights Stefan F. Wirth 2015/18

 

Astigmatid mite with a strict relationship to ants

 

The mite Forcellinia wasmanni is known to be strictly associated with ants (e.g. Türk & Türk 1957). It is clear that attaching young female alates would secure the dispersial of the mite into a new ant nest. It is not clear, which function the transport via ant workers can have. But Türk & Türk (1957) mention that the free living instars of Forcellinia wasmanni would feed on dead ants. Such a kind of microhabitat for the development is not unique in astigmatid mites. Some species within the Astigmata are known to have such preferences for decaying cadavers, but are then feeding on microorganisms, which grow on these (insect) cadavers. Ant workers might be ideal to carry mite deutonymphs to new cadavers, where they would leave and develop. Ants generally have a very well developed hygienic behavior. This guarantees the mites to get access to cadavers regularly. I do not know any other video footage, showing living deutonymphs attached to their carriers on such a magnification level as visible in this film. The original footage of these deutonymphs is much longer.

 

Morphology and behavior of the dislersal-instar, the so called „deutonymph“

 

The function of the proterosoma (dorsal shield of the forebody) is acting as a flexible structure, protecting the mouthpart-area (non-functional in deutonymphs) and the fore-legs, but being very motile and being easily pushed backwards (under the following hyterosoma-shield), when the mite lifts up from the surface of the ant pupa. I cannot state much more concerning the second mite, found on pupae, which is a species of the Gamasina. I discovered this phenomenon only on three of my pupae. Ant nests represent complex communities of organisms, to which fungae, other insects, mites and nematodes can belong. The samples visible in this film were collected in July 2015 on the German island Usedom inside a forest area between the villages Zinnowitz and Karlshagen. The ant nest was quite small. An ant hill was not visible.

 

Complexity of life in ant nests

 

The complexity of life within ant nests is a result of evolution. I am an enemy of creationistic movements, including all modern faces of creationism. Creationism stimulates carelessness und illiteracy in the believing people.

 

 

Berlin August 2015/ December 2018, copyrights Stefan F. Wirth

Habitat compost: Mite Histiostoma sachsi carries old cuticle and dirt as camouflage

My parents have a compost area in their backyards. I use it as reference habitat for two mite species of the family Histiostomatidae (Astigmata): Since I began my research in 2000, the compost regularly contained Histiostoma feroniarum with its typical male dimorphism. Since summer 2017 another species appears additionally regularly: Histiostoma sachsi. Both species do not appear under the same conditions. While H. feroniarum prefers fresher decaying material, H. sachsi on visibly older decomposed tissue. There mite be even more mites of the Histiostomatidae exist in this complex compost habitat, but under my laboratory conditions, only the two named species were so far successfully reared out of samles always again. Regarding the determination of H. sachsi on a species level, I was more careful in my comments to a former video (June 17), in which I named it Histiostoma cf. sachsi due to doubts about a correct identification. Meanwhile, also due to the morphology of the deutonymph, I determine „my“ compost mite as Histiostoma sachsi Scheucher, 1957. But it is still to emphasize that Scheucher described H. sachsi from cattle dung, not from compost. But generally, both habitats can sometimes share the same inhabitants.

 

Adult females carry their old cuticles and „dirt“ on their backs as tactile comouflage

 

Biologically conspicuous is darkish material, which especially adult females carry on their backs. Unlike males, females posses elongated setae on their backsides. These setae support the holding of material such as old cuticle and soil particles. In slide preparations, this cover usually appears amorphic and contains substrate from the mite’s environment. My video footage indicates that the basis of this cover is a retained old cuticle from the former nymphal instar . That this cannot easily be proven with the light microscope is due to the very soft and fine character of the cuticles in these mites. Remnants might become decomposed by microorganisms after a while.

Compost: the habitat of the mite Histiostoma sachsi Scheucher, 1957 (Acariformes, Astigmata, Histiostomatidae). Copyrights Stefan F. Wirth, please like my video also on youtube, in case you like it.

 

The phoretic dispersal instar, named deutonymph, in mites of the Astigmata controls its body position due to sticky leg endings and suckers on their undersides

 

Deutonymphs of H. sachsi represent one of my resent models to study mite-dispersal behavior. My research focus since a while concerns ultrastructure and function morphology of the deutonympal suckerplates and other structures to attach to insects for dispersal (this dispersal strategy is called phoresie). The anterior front-suckers on the suckerplate of the mite’s underside is extendable and very flexible, not only to find a suitable position on the insect carrier. When falling, the deutonymphs use it to lift their bodies up into a proper position again. Additionally they will try to get hold using „sticky“ lobe-shaped setae on the endings of legs I and II. Both is visible in my footage. The forelegs seem generally to make the first contact, when trying to get on a suitable carrier.

 

Deutonymphs of Histiostoma sachsi take a ride on other mites (Oribatida)

 

The suitable carrier of H. sachsi is unknown to me. Some astigmatid species have even a range of carrier-„hosts“. In my samples, deutonymphs at least attach to other mites, especially to mites of the Oribatida. This is in a very short scene visible in my video too.

 

Copyrights Stefan F. Wirth, Berlin December 2018

A scarab beetle’s larva and pupa: habitats for mites and other organisms

The micro-world is complex. Its habitats intertwine themselves, some even are unusual, because they are formed by single animal individuals. An example is a holometabolic insect, here the tropical rose chafer Eudicella colmanti. The larvae of my specimens are covered with deutonymphs of an astigmatid mite (Acaridae, eventually Acarus sp.).

This makes the beetle larva to a habitat for these mites, although the mites in this case don’t feed or reproduce there. They instead are „only“ passengers on their transportation to a new „real“ habitat, where they become adult, feed and reproduce. This strategy to be carried by other organisms from one living place to another is called phoresy.

The situation in my terrarium might be artificial in the sense that mites are putatively not of tropical origin as the beetles (reared in Germany) and thus do not originally „belong“ to the beetle species. The mites might have reached into the terrarium via fruit flies or similar native organisms or via the terraria of the online shop, where they were bought. But the mite deutonymphs show a distinct affinity for adult beetles and their larvae nevertheless, which they attached in great numbers (not the pupa). The microscopic footage of the mite deutonymphs contains activities of their genital openings, located close to the sucker plates on their undersides.

They occasionally open and close and discharge secretions or water. This might be due to osmoregulation and/or in order to prove the adjacent sucking structure with moisture for a more stable hold.

The larva after some months built its pupa chamber, consisting of soil particles and larva secretions. Tese pupa chambers offer on their outer sides obviously enough nutrients for collembolans, which appeared there in greater numbers, especially on an older chambers with its pupa waiting to hatch. Mites of the Gamasida and tiny annelids could also be observed there. The video consists of macro fotage and microscopic footage, all recorded in 4K and rendered in an uncompressed quality.

 

Berlin, December 2017/November 2018, copyrights Stefan F. Wirth