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Kategorie: Wissenschaft

Locomotion behavior of Schizomida (Arachnida)

They look without magnification more like very motile and fast running ants or very tiny grasshoppers than like arachnids. But they indeed represent relatives of the web spiders and scorpions: Schizomida, a clade of whip scorpions. They are the sister taxon of Thelyphonida, the rather well known „big whip scorpions“, which are often kept as pets in terraria around the world. Schizomida are only rarely filmed in a higher resolution quality, which is due to their small size and their almost invisibility due to their semi-transparent cuticle and their very fast way of walking or even jumping. They are additionally difficult to be filmed as they strictly avoid all lights and tend to dry out quickly, when they cannot hide themselves by time in a slightly moist substrate.

 

Closeups of behaviors of a Schizomid species from a greenhouse in Germany. Copyrights Stefan F. Wirth

 

Schizomida in Greenhouses

 

Schizomids represent mostly tropical or subtropical organisms. But some species are regularly dispersed into greenhouses around the world. The filmed species might be Stenochrus portoricensis, but was not systematically studied in detail so far. As all known species, which appear in greenhouses, also S. portoricensis reproduces (apart from their original habitats) parthenogenetically with females producing females without mating procedures (thelytoky). I never found males so far.

 

 S. portoricensis: native to subtropical Zones

 

The specimens, which I kept since months in a small terrarium, were collected in autumn 2016 at the famous fun and wellness bath „Tropical Islands“ South of Berlin. There they are a natural part of the world’s biggest indoor rainforest. The species S. portoricensis is originally native to Florida, Mexico, Cuba, Nicaragua, Porto Rico and other localities in similar tropical zones. These microscopical tiny organisms are predators and do not harm human beings at all. According to the available organisms in a suitable size in my terrarium, they might feed on the numerous collembolans and/or mites. Especially mites of the Gamasina appear in greater numbers in my substrate, which represents the original substrate from the greenhouse. I enriched this substrate regularly by smaller pieces of fruits or vegetables to stimulate the growth of microorganisms. I keep them at room temperature (about 20°C) and with not too much moisture. I do not know, whether they reproduced within these months, but the specimens of my recent video footage represent all sub-adults.

 

Film set and topic locomotion

 

Focus of my film is to present the different ways of locomotion, cleaning behaviors and burrowing activities of these fascinating animals. During the filming procedure, I used two cold-light-lamps for a suitable illumination and an ILCE-6300 (internal 4K mode), connected to a stereomicroscope and a lightmicroscope (with uplight).

 

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

When elbows are used in the world of science

I was part as acarologist and natural scientist in a 2011 scientific paper about a mite preserved as fossil in amber, which was analyzed using the X-ray computed tomography and determined systematically on a family level. In this time, this scientific publication had a remarkable impact in international scientific media, because it seemed, as if this mite was the smallest animal ever visualized via CT on a high quality level.

 

Strange behaviors of so called „colleagues“?

 

The technical work was performed by technical scientists in Manchester UK. The natural scientific analyses was performed by me as the only European specialist for the mite family Histiostomatidae. But I noticed already in the time period of  this publication that there were strict tendencies by the so called „colleagues“ to mention my name as less as possible, this concerned the drafting of international media releases and also a poster presentation (my name was added days later) and an online abstract on a conference in Berlin. The corresponding poster was even awarded, but I got my award certification only after demanding explicitly for it. I much later, when I decided to complain officially at the Museum of Natural Sciences in Berlin, needed to learn that I was not even considered as one of the first authors. I didn’t notice that before, because the former „colleague“, Dr. Jason Dunlop, curator at this museum, was mentioned in the original citation with 1) after his name, me too. Thus I interpreted this as a double-first-author-ship. It then came out that the „1)“ only indicated the same scientific address, because I was in that time officially a volunteer at the MFN in Berlin.

 

Mite in an amber fossil, made visible by using the x-ray computed tomography, acarological work: Stefan F. Wirth

 

The work of a scientific specialist: here an acarologist

 

The question must be: Who is needed to scientifically interpret three dimensional photos of an amber fossil, in this case the deutonymph of a mite of the Histiostomatidae? A specialist for this taxon is needed, who is able to perform scientific drawings, based on the photos. He first needs even to decide, which of the photos are showing details of scientific relevance. While drawing, the specialist must distinctly recognize single microscopic structures, so that all these structures can be clearly separated from each other including all borders or gaps between single components. The scientific term is „homologisation“. Homologisation means: comparing single structures with (phylogenetically) equivalent structures of other (related) species. As there were not more fossils available, the homologisations needed to be based on recent mites. Thus the specialist must have a very competent knowledge of a high number of species from this family. To reach that level requires hard work over many years. I had the necessary level and found character details in the fossil, which were fitting to recent members of mites of the Histiostomatidae. But it’s of course not enough to discover such homologous structures. They must be made visible for every reader of the scientific paper. Thus the drawings need to be correctly labelled, which requires careful morphological studies. Then a detailed description needs to be written. But that is far not enough. Readers of a scientific paper are usually no specialists. That’s why they need a written introduction, in which the summary of the general recent knowledge of a mite group needs to be presented. And after all that they even expect you to discuss your results. It’s an own chapter, subsequent to the result descriptions.

The discussion chapter also requires a maximum of specialized competence. Some researchers even say that this is the first part of a paper that they read as it puts the results into a general scientific context based on arguments, mostly according to the principle of the most economical explication. Conclusions in the discussion part have usually the character of theories based on the facts, which the paper could contribute. Topics of a discussion part in such a paper as ours are systematic conclusions, the discussing of homologisation problems and also the formulation of a possible relevance for the recent scientific knowledge and also the future scientific importance of these new findings.

This all is, what I as a specialist needed to do. I additionally contributed one of my photos of a recent mite for comparative reasons and captured a stereomicroscopic photo of the mite fossil to demonstrate, how much the CT could improve the visible details of the amber fossil. I guess I did quite a lot, the other part was overtaken by the technical colleagues in Manchester. They needed to explain their technical situation and also needed to discuss their ideas about the meaning of their CT-technology for the future of science, focussed also on work with amber fossils.

 

Contributions of different authors to a scientific paper

 

To be honest I don’t remember, where there was still space left for content issue contributions by Dr. Dunlop. But he did some organizational stuff, he collected the contributions from the UK colleagues and me, he arranged the photo table via a graphic software based on the photos, which I had determined as scientifically relevant, and he was the so called corresponding author (I allowed him, because he is an English native speaker). That means, he submitted the final paper to the journal and communicated with the editors. Of course reviewers always ask for revisions. That was then mine and the technicians job again.

It is common that corresponding authors represent automatically the first authors of a paper. But it is not mandatory. I for example once was the corresponding author of a paper, which was based on a bachelor thesis that I (in major parts) supervised. I despite of my in fact major authorship regarding the scientific paper itself and my additional corresponding activities let her (the student) the first authorship. That even means that this paper can be easier found, when searching for her instead of my name. I just wanted to support a younger scientist.

And of course also a double first-authorship might be possible, especially representing  an adequate solution, in case another author even contributed more concerning the scientific content itself. In case of objections by the editors, the one, who contributed more, should to be the first author.

 

„B-word“?

 

But to come back to the amber paper of this article, it is surely not fair to reduce the scientist, who had the major scientific work on a paper secretly to a second author. It is highly unfair to leave him out in the international press release information. And I don’t trust to say here, what it is, when deleting his name entirely from a poster and an online abstract presentation and even impeding him to get a certification of a poster award in time for his work. Should one use the „b-word“? Generally bullying would be an act against the good scientific practice, but there would be clear proofs for malevolence against specifically somebody needed to get corresponding behaviors sanctioned. But when „only“ the elbow mentality is obvious, which means that people leave somebody out for their own better recognition, then the distinct malevolence against the victim is not clearly proven. Thus the interesting question arises: when is elbow behavior equal to bullying and when not?

 

Warning to young scientists

 

What I can say for sure is, even when the original bullying assumption is still a kind of questionable: after you complained, you might need to expect a real merciless and long lasting bullying. That’s why I intend to warn all young scientists: be careful and double check, with whom you cooperate. The wrong choice can be a failure as long as you do not agree being a bullying victim. The consequences can last over years and can destroy your whole career. I even once was told by a bullying victim that the accused institution did not even deny its bullying activities, but stated that depending of the kind of position, somebody has in an institute, an equality right would not be automatically existent. I go further and say: don’t become a natural scientist at all, except you are in a love relationship with an internationally highly influential professor.

In these days there are alternatives for possible natural scientists. Earlier I was a harsh critic of the modern gender sciences (sometimes also named genderism). But they have much financial capacities. Nobody there needs to sharpen his elbows, a good basis for fair careers, and based on that after a while surely also the most important basis for a good quality work!

 

Copyrights Stefan F. Wirth, Berlin 2019

 

Drone flights: Worth seeing nature around the fields of Berlin

The metropolis Berlin is the capital of Germany and much more than that. It represents an unusual green city. When using elevated viewpoints to watch the cityshape, then at least in summer visitors of Berlin can receive the impression of being in the midst of a greening huge landscapes with several villages in between.

 

Green areas in Berlin

 

 

Indeed related to other metropolitan cities of the world, Berlin is still partly not very densely populated and covered by remarkable huge natural countryside instead. The area of landing and runway strips of the former airport Tempelhof for example up to date represents the largest coherent green area inside a city worldwide. The so called Tempelhofer Feld was after the termination of the air traffic exposed to renaturation and is currently a very popular recreational park. It’s located in the South of the city.

Also the West and South-West partly represent nature reserve areas and are covered by the big urban forest Grunewald.

 

Meadows and wetlands in the North of Berlin as nature refuges

 

I am since two years discovering the Northern parts of Berlin, which according to my random observations (in comparison with other Berlin areas, such as Tempehofer Feld, Teufelsberg (Grunewald) and some urban parks in the center of the city; examples of species will be visible on my corresponding blog article) bears the greatest biodiversity in bloom visiting insects.

 

 

 

Mosaic of different landscape types close to each other

 

 

 

 

 

This is seemingly due to the complexity of different meadow-, field-, wetland- and bog-habitats, being originally shaped by the Weichselian-glaciers. I regularly visited the stream valley of the so called Tegeler Fließ with the lake Köppchensee. It’s a hilly area with different gradients of sunny slopes with partly Mediterranean climatic conditions, surrounded by different kinds of wetlands. This area is well known for its great biodiversity.

 

Between the villages Rosenthal, Lübars and Blankenfelde

 

But my drone flights present vast tracts in the South of that stream valley, consisting of fields, green meadows and wetlands. It is the area between the Berlin villages Rosenthal, Lübars and Blankenfelde. Inner urban agriculture is rare in metropolian cities worldwide, in Berlin there is only a small agriculture area in the South (Dahlem Dorf) and the fields between the named villages in the North.

 

Drone flights and bloom visiting insects

 

 

Fields and meadows with adjacent forests and wetlands in the North of Berlin, September 2019, copyrights Stefan F. Wirth. Please give my video also your like on Youtube.

 

Most part of the footage in my film represents the fields adjacent to the village Rosenthal. I newly discovered the partly quite tiny meadows between and adjacent to agricultural fields around Rosenthal this summer and discovered an impressive and steadily visible diversity of bloom visiting insects there. Fields as monoculture habitats usually bear a smaller biodiversity related to wild-growing nature zones. But due to the connection of the edges of fields with complex nature refuge zones around, I could observe a quite great number of species on closely adjacent meadows and even the natural border zones of these agricultural areas.

 

Videographic details

 

The footage was captured in 4K and D-cinelike quality using a Mavic 2 Zoom drone between September and October 2019.

 

 

Berlin, September/ October 2019, copyrights Stefan F. Wirth

 

Different wing colors in a harlequin ladybeetle specimen

The ladybeetle Harmonia axyridis is naturally distributed over eastern Asia, but was imported to the United States already at the beginning of the 20th century as pest control. At first, there was no population development in the open fields. These were at first reported from Louisiana in 1988. In 2001 the first free living specimens were for Europe discovered in Belgium. Since then the beetle distributed over several European countries, such as France, entire Germany or Switzerland.

 

Variations of Harmonia axyridis

 

The beetle is well known for its great form variations. Worldwide more than 200 different color pattern forms of thorax and elytrae are described. They are distinctly shaped and maintain in this shape and arrangement of pattern. But four forms dominate within natural populations. Speaking about the elytrae (not the thorax patterns), the reddish form with dark spots, as visible in my film, is one of them.

These distinct different forms must be named a polymorphism and are based on genetic information as well as on environmental conditions, such as temperature, humidity and light intensitivity. According to that even the term polyphenism might be adequate.

 

 

 

 

Transcription factor pannier responsible for color pattern polymorphism

 

According to the work of M. Gautier et al. (the genomic basis of color pattern polymorphism  in the harlequin ladybird, Current biology, 28, 20), the transcription factor pannier is responsible for the genetically based control of this polymorphism. They discovered that different pannier alleles determine the color pattern in the different known forms. The authors furthermore report that pannier was never found before to play a keyfactor role in the pigmentation of insects.

 

Ladybeetle species on a meadow in Berlin

 

The specimen in my footage was discovered on an urban meadow in the park area „Nordhafen“ in Berlin. It’s a meadow in autumn predominantly consisting of lucerne and clover, sorrel and yellow field cress. Different ladybeetle species could be in greater numbers found there between September and October 2019. The sevenspot-ladybird, the adonis ladybird (Hippodamia variegata) and most abundant the harlquin ladybird in all its developmental stages.

 

Asymmetrical wing colors and possible explications

 

 

Harlequin beetle specimen from Berlin with asymmetrically colored wings, copyrights Stefan F. Wirth, please like my video also on Youtube

 

The most conspicuous character of „my“ harlequin ladybird specimen was its distinct asymmetrically colored wings (elytrae). One side reddish with black spots, the other side brownish with black spots. During my research about such asymmetries in ladybirds, I didn’t find recent studies, which distinctly focussed on that topic. H. E. Roy et al. reported in their book „ladybirds“ (original version 1989, revised version 2013) about the existance of such differently colored wings in the same specimen. They emphasized that the phenominon was not studied in detail, but assumed different factors being eventually responsible for such a development of a beetle individual: 1) disruption of pigment production, 2) mitotic mutation in early development, 3) environmental conditions, eventually influencing the colors of an originally normal developed young adult (exposed for longer time to different light intensities etc.). The latter might in the case of „my“ specimen being an indeed possible factor, as it is clearly visible that also the brownish wing has at its edges some of the reddish pigments.

 

 

Filming/ photography conditions

 

The beetles was filmed and photographed under artificial conditions in a soil and grass-set in my video lab. There, mites of the Gamasina (Parasitiformes, evtl. mostly Laelapidae) were common. They interestingly showed a phoretic behavior by quickly climbing onto the wings of that ladybeetle. They obviously recognized it as a suitable carrier to new habitats. I assume ladybeetles in the field not being of much attraction for phoretic dispersal, based on their life-cycles and preferred habitats.

 

Berlin, September/ October 2019, Copyrights Stefan F. Wirth

Diving, feather cleaning and water bathing of the Inca tern Larosterna inca


Inca terns live along the South American Pacific coast and breed along rocky coastlines of Peru and North Chile. They can be easily identified by their grey plumages, their distinctly red beaks and feeds as well by their conspicious white feather curls on the bases of their beaks.

 

Geographic distribution and life-strategy aspects of Larosterna inca

 

Larosterna inca breeds inside rocky walls of coastlines either inside rocky cavities or in old nesting holes of other seabird species. Its hunting ground is the  Humboldt Current, which is famous for its cold temperature, but also its enormous fish wealth. To increase its chances for fishing success, the Inca tern might follow sea lions, cormorants and whales  and is then hunting fishes, which were flushed up by these bigger sea animals. They also follow fisher boats to catch some rests of their fishery.

 

Phylogenetic (systematic) relationships

 

According to phylogenetic reconstructions L. inca, which represents the only recent species of its genus, branches off in the Animalia tree within the monophyletic clade of terns. Based on DNA sequences E. S. Bridge, A. W. Jones and A. J. Baker reconstructed in their 2005 paper (Molecular phylogenetics and evolution) a sister-clade relationship between Larosterna and species of the taxa Sterna, Thalasseus and Chlidonias (mitochondrial DNA was used to reconstruct the tern phylogeny).

Terns themselves seem representing an own clade (Sternidae), being for example based on characters of behavioral pattern, and are considered as a sister taxon of gulls (Laridae).

 

Filming conditions and filming locality

 

My footage was recorded in the Zoo Berlin, where terns together with other sea birds inhabit a for tourists accessible free-flight enclosure. There I captured scenes about the diving and „fishing“ behavior (specimens fished repeatedly wooden sticks) as well as their plumage cleaning activities on shore and their conspicuous plumage cleaning behaviors via extended bathing trips inside areas of low water. Size of my entire video is 4K. But parts of the scenes were originally recorded in Full HD to enable a better slow motion effect based on 100 frames per second. Such footage was subsequently digitally magnified into the 4K size to fit in the entire video project.

All behavioral activities are at first presented in a slow motion (ca. three to four times slowlier than  original speed), then in the much faster original speed.

 

Plumage cleaning

 

Plumage cleaning is part of the hygienic behaviors of birds. Feathers can only stay in full function, thermoregulation and flying, when dirt and parasites are removed regularly. Typical plumage parasites are represented by feather mites (no phylogenetic clade), which consist of taxa of the Astigmata (Acariformes) and of taxa of the Dermanyssoidea (Parasitiformes). Feather lice represent  a subclade of the (Phthiraptera = lice), named Mallophaga. The monophyletic situation of Mallophaga is seemingly doubtful.

 

Plumage cleaning and hunting behavior of Larosterna inca, video (4K9, copyrights Stefan F. Wirth. Please like my video on youtube too.

 

Putative reasons for plumage cleaning behaviors

 

I couldn’t research sufficient information about specific plumage parasites of Larosterna inca. There is indication that terns generally are relatively free of predators and parasites. Seemingly, plumage parasites of this particular species are still a more or less open research field. But the existence of a regular and visibly careful plumage cleaning might indicate a sensitiveness for corresponding parasites. L. inca can be according to literature (e.g. W. Pieters et al., Avian Diseases, 2014) fatally infested with the trematode Ichthyocotylurus erraticus.

 

Copyrights Stefan F. Wirth, Zoo Berlin July/ September 2019

Mite Histiostoma sp., putatively new species, from mud around ponds (Berlin) and its morphology

Gravel pit area „Im Jagen 86“ in Berlin as biotope

 

„Im Jagen 86“ is a former gravel pit area in the Berlin urban forest Grunewald. It today represents a dynamic biotope, consisting of different types of habitats: mud around ponds, sand dunes, dry grassland and forest. Since the early 2000th, its habitat composition partly changed remarkably. Out of several (smaller) ponds, only one bigger pond remained. All ponds originally were surrounded by sapropel, a habitat for different interesting organisms, such as beetles of Heterocerus, Elaphrus and Bembidion. The mite Histiostoma maritimum was commonly found phoreticaly on Heterocerus and Elaphrus. I additionally in those early 2000th described the new mite Histiostoma palustre from Hydrophilidae of Cercyon and Coelostoma, living inside the saporopel as well. Today only a few small areas with open sapropel exist. I so far did not look for Histiostoma maritimum again and don’t know, how common it still is. At least Heterocerus beetles are harder to find than in earlier years. I so far did not found Histiostoma palustre again.

 

Rearing conditions of a putatively new mite species

 

I collected new mud samples in March 2019 at different areas, but found developing histiostomatid mites in a sample from the edge between mud (sapropel) and mosses. It is a species I never found before there and which might represent a new species. Only females could be morphologically studied. Nymyphal stages (not deutonymphs) are only available as video footage. No males were found. I had added bigger potato pieces to stimulate microorganism growth as mite food into the soil sample (room temperature). After about one month, a few mites (females and proto/tritonymphs) developed on only one of these potato pieces and quickly died out shortly after my filming activities and after I could prepare a few females. I actually try to get them reared again. Due to the low temperatures in March, it is considered that these mites hibernate independently from insects in the substrate. No bigger insects could be found in the substrate, which might be the corresponding carriers. But different dipterans (e.g. Ceratopogonidae) developed, they had no mite deutonymphs after hatching in my sample.

 

 

 

 

Morphological reconstruction of females and important characters as well as behavioral observations

 

The females of Histiostoma sp. differ from other females, which I know, by the mosaic of the following characters: body conspicuously elongated with a distinctly big distance between hind ringorgans and anus, digitus fixus almost simple shaped, fringes or ridges on palparmembrane, 6 dorsal humps, unusually big copulation opening. Leg setation not yet studied. One pair of ventral setae hardly visible (not in the drawing). Nymphs were observed during burrowing activities (footage), females are may be also able to. Deutonymphs or males would be useful to decide, whether the species is new. Some species are only described by deutonymphs.

 

Berlin, March/ June 2019 All copyrights Stefan F. Wirth

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

Late winter insect life: winter aconite blossoms and dipteran visitors

When do the first insect activities in the new year occur? Can insects be active in winter, even in the presence of snow? The answer is generally yes, different insect species even use to appear on warmer winter days on top of snow layers. Examples are the limoniid crane fly Chionea belgica, a wingless dipteran, which can be observed on milder winter days on snow surfaces along forest edges in Central Europe. Also the fly Trichocera hiemalis belongs to the winter crane flies (Trichoceridae) and can be characterized by a very well developed cold resistance. It appears on sunny winter days between branches of leafless trees in swarms around invading sunlight beams.

 

The winter aconite as an early blooming flower and its biology

 

But what about insects, visiting blooming flowers? This requires the existance of early blossoms, which can grow and bloom under winter conditions. A well known example is the winter aconite Eranthis hyemalis, which outlasts the summer period only by its underground tubers. Their conspicuous yellow blossoms belong to the first blooming flowers in the year. In Central Europe, they begin to grow under suitable conditions in mid February. They require milder temperatures, but even persist in case an unusual cold snap would happen. The blossoms open only at sunshine and thus close shortly after sunset. Opening and closing is a growth process, which depends on temperature conditions. Such a phenomenon is called thermonasty.

 

The winter aconite as a neophyte in Germany

 

In Central Europe, such as in Germany, E. hyemalis is a neophyte. It is originally native to Southern European areas, Turkey, South-East-France, Italy, Bulgaria and Hungary.

The species was introduced to Central Europe (and North America) as ornamental plant for gardens. It is proven that it was in Germany already cultivated since the 16th century. The German botanist, nature researcher and medical doctor Joachim Camerarius reared the winter agonite, which he brought from Italy, since 1588 in his backyards.

 

Common pollinating insects

 

Pollinating insects of E. hyemalis are flies, bumblebees and bees. To reach the nectar inside the blossoms requires a proboscis length of about two mm, which is mostly given in bumblebees and bees.

 

Flowerbed in Berlin urban park Schillerpark

 

I documented via my videography (4K) and photography a smaller area of winter aconites in front of a wall at urban park „Schillerpark“ (honoring the German poet Friedrich Schiller) in Berlin. The bright bricks of that wall reflected efficiently the solar warmth and thus created suitable conditions for a late winter flowerbed full of life.

 

Video with winter aconite blossoms and pollunating flies, copyrights Stefan F. Wirth.

 

Most abundant insects in that winter aconite bed

 

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Western honey bee, copyrights Stefan F. Wirth

 

The western honey bee Apis mellifera was often seen on blossoms, but unfortunately was not captured via video footage. Our honey bee hibernates in a so called winter clusters with lower temperatures and low activities in workers. Beginning in late winter/ early spring, workers increase the nest temperature due to body movements up to 35°C. This is exactly the body temperature, workers need to fly out and collect first nectar and pollen, for example from the winter agonite.

 

Drone fly on blossom of the winter aconite, copyrights Stefan F. Wirth

 

The drone fly Eristalis tenax belongs to the hoverflies (Syrphidae). Their larvae develop in watery environments, where they use their conspicuous snorkel tube to breath air at the water surface. Adults are typical blossom visitors, preferring Asteraceae and Apiaceae. Interesting highlight of their biology is the migratory behavior. These migratory insects form swarms, which cross the Alpes towards Southern European areas by using suitable wind conditions, where they finally hibernate and reproduce. The next generation returns the same way back. Not all individuals participate these migratory flights and would try to hibernate in Central Europe. Hibernating individuals are always females, which were fertilized prior to their winter diapause or their migration and which lay their eggs in the subsequent spring or in southern regions during winter. In Germany they only survive in greater numbers in milder winters, which they persist in temperature-stable hideways, such as gaps inside walls or wooden habitats. These specimen can be usually observed early in the year, beginning with March, when visiting blooming flowers. Their numerous very early appearance in mid February 2019 might be due to a very warm summer 2018 and a subsequent very mild winter in north-eastern Germany (Berlin). I have no comparative findings regarding the usual blooming time of the winter aconite and the abundance of drone flies there for Berlin or even this specific urban park. I also don’t know about indications that due to a global warming, as in some migratory birds, less specimens of the fly would migrate and more stay to hibernate here around.

The research station „Randecker Maar“ in the Swabian Jura records changes in migratory flights of birds and insects. They discovered a distinct decline of numbers of migrating drone flies and interpret it as a result of the increasing application of poisonous substances in the agricultural sector. Whether they additionally consider this being due to more individuals hibernating, where they are, based on generally warmer temperatures (global warming) is unknown to me.

 

Blow fly on blossom of the winter aconite, copyrights Stefan F. Wirth

 

The blow fly Calliphora vicina is a common blossom visitor in early spring and autumn. This fly, typically appearing in human settlements in Europe and the New World, is well adapted for an activity at lower temperatures (more than 13°C). While larvae develop in decomposing organic tissue (such as cadavers of animals), adults feed on nectar and pollen. They additionally incorprate saps from organic material with a strong odor.

C. vicina produces about five generation per year and throughout the year. The flies can even be active in winter, when temperatures reach a suitable level.

 

Other fly species were existant, but I did not determine them.

 

Time of footage and photo recording

 

Video footage and photos were recorded between 16 and 18 February 2019 in the urban park Schillerpark in Berlin.

 

Copyrights: Stefan F. Wirth, Berlin 2019.

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.

 

Arapaima gigas, einer der größten Süßwasserfische – doch was sind Fische eigentlich?

Sie sind beeindruckende Fische, nicht nur aufgrund ihrer Größe. Und doch kennen die meisten Menschen sie nur aus den Aquarienhäusern zoologischer Gärten. Arapaima gigas wird mindestens zwei Meter lang und erreicht in Ausnahmefällen sogar Längen von über drei Metern. Beheimatet ist die Art im Bereich des Amazonas-Beckens und ist in Peru, Brasilien und Guyana verbreitet.

 

Arapaima gigas, einer der größten bekannten Süßwasserfische aus dem Amazonas-Gebiet

 

Arapaima ist ein Räuber. Erwachsene Fische ernähren sich von anderen Fischen sowie Tieren in vergleichbarer Größe, wie zum Beispiel auch kleineren Säugern. Besonders auffällig sind die kräftig gestalteten großen Schuppen, die den Körper der Tiere umschließen. Sie dienen unter anderem als mechanischer Schutz gegen Angriffe durch Feinde. So können sie beispielsweise den Attacken der im selben Lebensraum beheimateten Piranhas, die zwar wesentlich kleiner sind, aber bekanntlich empfindliche Beißwerkzeuge besitzen, wirkungsvoll widerstehen. Das schützt Arapaima freilich nicht vor seinem größten Feind, dem Menschen. Er ist ein beliebter Speisefisch, der durch massenhafte Bejagung in seinem Bestand immer wieder gefährdet wird.

Arapaima gigas wird häufig als größter Süßwasserfisch der Welt bezeichnet. Dies basiert jedoch auf Übertreibungen. In Wahrheit befindet er sich in der Größenordnung des Europäischen Welses, dem größten europäischen Süßwasserfisch.

 

„Fische“ ist keine spezielle systematische Gruppierung

 

Ich verwendete bislang stets unkommentiert den Begriff „Fisch“. Was sind Fische eigentlich?Welche sogenannte Fische kennt man noch? Wie verhält es sich beispielsweise mit dem Bullenhai, der über drei Meter lang werden kann und neben marinen Habitaten auch im Süßwasser auftreten kann. Kann er als Gigant des Süßwassers mit dem Arapaima, dem Gigant aus dem Amazonas verglichen werden? Nach evolutionsbiologisch-systematischen (=phylogenetisch) Gesichtspunkten kann er das nicht. Der Begriff „Fisch“ bezeichnet nämlich keine spezielle, systematisch in sich geschlossene Gruppe. Stattdessen haben wir es mit einem deskriptiven Begriff zu tun, der alle Tiere umfasst, die in ihrer Gestalt ganz grundsätzlich eine gewisse Ähnlichkeit mit dem Goldfisch aufweisen.

Wenn wir außer Acht lassen, dass auch „Tintenfische“ und „Walfische“ nach demselben Muster benannt wurden, die bekanntlich zu den Mollusken und Säugetieren gehören, weist die Fischgestalt zumindest in den meisten Fällen auf eine irgendwie gestaltete Verwandtschaft hin. Jedoch sind Haie und Arapaima dennoch nicht sonderlich nahe miteinander verwandt.

 

Arapaima gigas im Aquarium des Zoos Berlin, ein gigantischer Süßwasserfisch, der regelmäßig atmosphärische Luft an der Wasseroberfläche aufnehmen muss. Copyrights Stefan F. Wirth

 

Bei den „Fischen“ handelt es sich nämlich um eine sogenannte paraphyletische Gruppe. Das heißt, sie umschließt zwar eine ihnen allen gemeinsame Stammart, jedoch keineswegs alle dazu gehörigen Tochtergruppen. Dazu würden nämlich auch alle Landwirbeltiere gehören. Eine vergleichbare paraphyletische Gruppe stellen beispielsweise die „Reptilien“ dar, zu denen Eidechsen/Schlangen, Schildkröten, Krokodile und alle Dinosaurier gehören. Da die Vögel aus den Dinosauriern hervorgingen, jedoch nicht zu den „Reptilien“ gezählt werden, haben wir es unter dieser Bezeichnung wieder mit einer Stammart und nur einem Teil aller Tochtergruppen zu tun, die allerdings im Stammbaum der Tiere nebeneinander stehen und daher näher miteinander verwandt sind, so wie auch bei den „Fischen“.

Im Falle der „Fische“ (paraphyletische Gruppen werden häufig in Anführungszeichen gesetzt) verhält es sich so, dass die verschiedenen als Fische bezeichneten Gruppen neben nur ihnen eigenen Merkmalen auch unterschiedliche Merkmale aufweisen, die auf eine Ahnenlinie hin zu den Wirbeltieren zurückgeführt werden müssen. Was unterscheidet also Knorpelfische (zum Beispiel Haie) und Strahlenflosser (Actinopterygii = echte Fische) voneinander? Eine Frage, die so in der modernen Systematik, die stets nach Gemeinsamkeiten sucht, eigentlich nicht gestellt wird. Richtiger ist es, zu fragen: Welche Merkmale teilen die Knorpelfische mit den Landwirbeltieren (z. B. knöcherner Schädel, Kiefer) und welche die Strahlenflosser (z.B. Lunge). Wenn man dennoch über Unterschiede sprechen möchte, ist festzustellen, dass Knorpelfische noch keine Lunge, die mit jener der Landwirbeltiere homolog ist, besitzen, Strahlenflosser aber schon. Die Lunge ist also auf der Ahnenlinie der Knorpelfische hin zu den Strahlenflossern evolviert. Anders als die „Fische“ sind die Strahlenflosser, die ich hier auch als echte Fische bezeichne, sehr wohl eine geschlossene systematische Einheit (=Monophylum), die auf Merkmale einer gemeinsamen Stammart zurückgeführt werden kann, die nur dieser Gruppe eigen sind. Ein Beispiel ist die namengebende Gestalt der Flossen, die durch Flossenstrahlen durchsetzt sind.

 

Zuerst gab es Lungen, aus denen Schwimmblasen evolvierten

 

Die Strahlenflosser (Actinopterygii), zu denen neben unzähligen Arten auch Arapaima gehört, besitzen also in der Tat ursprünglich paarige Lungen als Respirationsorgane. Diese sind demzufolge nicht erst vor dem Abzweig der Lungenfische entstanden, die als nächste Verwandte der Landwirbeltiere gelten. Die dortige Neuerung betrifft, anders als der Name Lungenfisch vermuten lässt, die Evolution eines Lungenkreislaufs, den es bei urtümlichen „Fischen“ mit Lunge noch nicht gegeben hat.

Aber besitzen echte Fische (Actinopteryii) nicht Schwimmblasen und atmen ausschließlich durch Kiemen? Mitnichten. Ursprüngliche Vertreter der echten Fische werden beispielsweise durch die Flösselhechte (Polypteriformes) representiert, die paarige sackförmige Lungen besitzen und neben der Kiemenatmung daher auch atmosphärische Luft veratmen können. Diese beeindruckenden Tiere können sich mithilfe ihrer Flossen nicht nur an Land fortbewegen, sondern lassen sich (es gibt Experimente an Senegal-Flösselhechten) auch unter vorwiegend terrestrischen Bedingungen in Terrarien halten.

Erst innerhalb der echten Fische ist die Schwimmblase entstanden, die sich durch Evolution aus den Lungen heraus bildete. Die fachgerechte Beschreibung lautet daher: Lunge und Schwimmblase sind einander homologe Organe. Innerhalb der Actinopterygii gibt es einen evolutiven Trend, demzufolge die Schwimmblase bei urtümlicheren Vertretern (noch) der Atmung dient, bei evolutiv weiter abgeleiteten Vertretern hingegen nur noch die Funktion der Austarierung im Wasser übernimmt.

Allerdings ist es innerhalb der echten Fische oftmals schwierig zu entschlüsseln und noch immer Gegenstand phylogenetischer Studien, ob die Lungenfunktion einer Schwimmblase einen Hinweis auf Urtümlichkeit darstellt, oder ob sekundär aus einer Schwimmblase mit Tarierfunktion erneut ein Atmungsorgan entstanden ist. In der Evolutionsbiologie werden im Übrigen unabhängige Entwicklungsschritte stets als Konvergenzen bezeichnet.

 

Arapaima gigas veratmet mithilfe seiner Schwimmblase atmosphärische Luft

 

Auch Arapaima gigas ist ein Luftatmer, der auf den Einsatz seines zusätzlichen Atmungsorgans in Form einer Schwimmblase sogar angewiesen ist. Er ist ein obligater Schwimmblasenatmer, der atmosphärische Luft an der Wasseroberfläche mithilfe seiner Mundöffnung aufnehmen muss. Dies wird als Anpassung an den häufig sauerstoffarmen Lebensraum der Tiere interpretiert, die sich häufig in Überflutungszonen des Amazonasbeckens aufhalten, wo wenig im Wasser gelöster Sauerstoff zur Verfügung steht. Der Literatur zufolge muss Arapaima gigas alle fünf bis fünfzehn Minuten die Wasseroberfläche aufsuchen, um dort mit seinem oberständigen Maul Luft einzuschnappen.

 

Berlin, Februar 2019, copyrights Stefan F. Wirth