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

Male and female of Histiostoma sachsi and unsuccessful mating with a „stranger“

Mites of the Acariformes vary in very different forms and life-strategies. One taxon of very tiny and soft-skinned mites is named Astigmata. Within them the familiy Histiostomatidae is especially rich of species, most of them surely not yet described or discovered.

 

Modyfied mouthparts and a specific mode of dispersal

 

These mites feed on microorganisms using a complex mouthpart-apparatus with multifunctional abilities. They can be found in habitats, which dry out quickly. When it’s getting too dry, a specific instar of the mites takes a ride on insects or other bigger arthropods for dispersal to a new and fresh habitat ( strategy called Phoresy).

Histiostoma sachsi is one of numerous (often closely related) long haired (in females) species. It was originally in 1957 described from cattle-dung. I found it in compost.

 

Long upper-setation in females and tactile camouflage (mimesis)

 

Adult females are characterized by a long setation on their uppersides. They use them to hold parts of the old nymphal cuticle and soil particles on their backs. This seems to be due to a strategy named mimesis or camouflage. It’s a tactile camouflage as an optical sense in this kind of microhabitats plays almost no role.

 

Normal and unusual copulation position, trial of an interspecific copulation

 

Males mate their females via a dorsal copulation opening and thus need to ride on them. In H. sachsi, that copulation opening is located very close to the hind-edge of the body. That way it is even despite of the camouflage cover accessible. It seems even slightly being elevated out of the body surface in order to surmount adjacent soil particles. This is an adaptation of this particular species. It might share such morphological characters only with very closely related (not yet described) species In other members of genus Histiostoma, the copulation opening is usually more centered related to the hind body.

The copulation position requires that males insert their aedeagus („penis“) into the copulation opening. They additionally use their legs to grasp into the females body. That kind of leg arrangement and thus the whole copulation position can differ from species to species.

This is why copulations between members of different species already fail, because the right copulation setting does not fit, nor does the shape of the aedeagous. Nevertheless the phenomenon of unsuccessful trials for interspecific copulations can sometimes be observed in laboratory cultures. Such a trial is also visible in this video, where a male of Histiostoma feroniarum (also appears in my compost samples regularly) tries to mate a female of H. sachsi. It cannot even almost get in a proper copulation position and seems to hold on to the dorsal camouflage cover of the female. it could only remain in a transverse position related to the female body and thus not get access to the copulation opening, normal would be a longitudinal position with the sameame orientation of female and male.

Adult mites of the family Histiostomatidae (Astigmata) and a „false“ copulation. Copyrights Stefan F. Wirth, Berlin December 2018. Please like my video also at Youtube, in case you like it.

 

Chemical communication and chemo-sensitive leg setation

 

Mites of the Astigmata communicate and find their general orientation due to chemo-sensitive setae, mostly on legs I and II, which are named solenidia. They are even on the magnification level of my footage well visible on the male’s legs. Although a direct body contact is not necessary for a innerspecific communication by chemically interpreting scents produced from mite glands, the observed male in my video repeatedly was seeking for intense body-contacts and obviously „observed“ his conspecific while doing so with its first two legs. This might have intensified the perception of pheromones.

It showed this behavior also, when passing by the „false copulation-pair“ described above. It additionally seemed to invest power in its leg movements as if it would try to remove the „competitor“ on the female, in this case even belonging to another species.

 

Competitive fights between males

 

That mites of the Histiostomatidae can use their strongly sclerotized first legs to fight under each other for an access to a female is known to me from my older observations about the species Histiostoma palustre and Histiostoma feroniarum.

 

Origin of the compost samples

 

The compost samples were collected in SW-Germany (Saarland in October 2018). The footage was recorded in December 2018 in Berlin.

 

Berlin December 2018, copyrights Stefan F. Wirth

Western lowland gorilla: locomotion, eating and facial expressions

We humans are nothing else than a species of great Apes and thus belong to the clade of the primates. Gorillas and chimpanzees represent our closest recent relatives.

 

Relationship to Homo sapiens

 

In earlier times, it was even stated that the two chimpanzee species and the two gorilla species altogether were the sister-clade of the Homo sapiens. This is not the standard of knowledge any more. Due to molecular evidence and other characters, it could be reconstructed that chimpanzees alone represent the sistergroup of modern humans. Gorillas are sister-taxon of the clade consisting of cimpanzees and Homo sapiens.

 

Knuckle-walking

 

The consequence of this systematic scenario is interesting, as the conspicuous mode of locomotion that can be found in gorillas and chimpanzees, the so called knucklewalking, might have also existed in very „primitive“ and extinct human species.

 

Two gorilla species

 

Another newer finding is that the four subspecies of gorillas (western lowland gorilla, Cross River gorilla, eastern lowland gorilla and mountain gorilla) represent two species, the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei). Visible in my film footage are specimens of the western gorilla, more exactly western lowland gorillas (Gorilla gorilla gorilla) from the Zoologischer Garten Berlin.

 

Preferred habitats

 

Gorillas live preferably on the ground, but are also good tree climbers. An exception is the mountain gorilla, which seems to avoid tree climbing. Gorillas even do not avoid water, but only access  water bodies, in which they can stand.

 

Social structure

 

The social structure of gorilla groups can be simplyfied as consisting of one dominant male (silverback), his females and subadult specimens. In case several adult males remain in a group, only the dominant silverback is reproductive. The normal case is that adult males leave their groups, remain for a while alone and try to find access to a new group. Interestingly, in gorillas also females leave their groups after adolescence . As a result, females of a group are usually not closer related with each other.

 

Diet

 

Gorillas represent the biggest great apes, but usually are vegetarians, preferring fruits, seeds and leaves as food. To gain enough nutrients, they need to invest a major time of their daily activities with eating. It is still unknown, which role carnivorous food plays for these apes. Some were observed during „termite fishing“. It might be that insects and smaller vertebrate might enrich their diet. In order to grasp smaller food particles, gorillas possess a quite well developed hand motor-skills, as visible in my footage.

Western lowland gorilla filmed in Berlin Zoologischer Garten, copyrights Stefan F. Wirth, Please like my videos also on youtube, in case you like them.

 

Facial expressions

 

As all gorillas, also the western lowland gorilla is characterized by very well developed facial expression abilities. it’s a character, which they share with chimpanzees and humans due to a common evolutionary event in the early ancestor line of the great apes. A differentiated facial expression, comparable with the one of humans, requires a suitable innervation, skull muscle origins and specific numbers and shapes of facial muscles.

 

Culture and the use of selfmade tools

 

It was earlier thought that cultural abilities and the use of selfmade tools would be unique for humans. The modern primatology could proof that this is not true. Both characters evolved obviously in the ancestor line of the great apes. Especially chimpanzees and gorillas are known for using tools, for example in order to perform termite-fishing. The transfer of a specific knowledge or abilities via teaching to the offspring is named culture. Also gorillas are able to do so.

 

Berlin, July/November 2018, Copyrights Stefan F. Wirth

Isopoda: locomotion and aggregation behavior

Isopods represent Arthropoda. But they are no insects, no arachnids and no myriapods, although the glomerids or pill-millipedes can have a similar shape. Isopods are indeed crustaceans.  And the shape of pill-millipedes is a result of independent evolution (convergent evolution).

Isopoda represent a clade of the Malacostraca, whose members are originally native to aquatic habitats. Also isopods from the phylogenetic point of view represent aquatic/ marine organisms. But one clade, the Oniscidea, also named terrestrial isopods, evolved mechanisms to survive ashore.

The footage shows a species of Oniscidea of genus Porcellio from mediterranean habitats in Croatia. Land isopods retained their gills and thus usually prefer moist habitats. My model-isopods are reared in a terrarium, were they use to aggregate under moist pieces of bark.

As most terrestrial isopods, they are destruents and feed on decaying organic material. I add regularly pieces of fruits or vegetables and thus create conditions comparable with compost. Most of my footage is presented in slow motion.

I thank Jana Bedek, Croatian Biospeleological Society, for her determination of the isopods on a genus level.

Copyrights: Stefan F. Wirth, Berlin May 2017/ November 2018