Category Archives: Friday Fellow

Friday Fellow: Truncate Trapdoor Spider

by Piter Kehoma Boll

Today I’m bringing you a species that fascinates me and that I was willing to introduce for a while. Unfortunately, there isn’t much information available about it, that being the reason for my delay in showing it here. However, as new information seems unlikely to appear soon, I can only show it with whatever is avaible.

Named Cyclocosmia truncata, today’s fellow is a trapdoor spider found in the East of the United States and sometimes referred to as truncate trapdoor spider. As all trapdoor spiders, it is a mygalomorph spider, such as tarantulas, and lives in a tunnel that it burrows in the ground and that is covered by a trapdoor. Trapdoor spiders in general rarely leave their burrows and hunt prey at night by standing behind the closed trapdoor and waiting for a prey to pass nearby, then jumping out and capturing it.

A truncate trapdoor spider in southeastern United States. Photo by iNaturalist user jimstarrett.*

Because trapdoor spiders are highly sedentary, they are very vulnerable to predators and parasites that can easily find them by locating their burrows. Species in the genus Cyclocosma have developed a fascinating morphological adaptation to cope with that. Their abdomen is abruptly truncated, giving the impression that someone just cut half of the abdomen off. This region of the abdomen is covered by a heavily sclerotized disc. When the spider is not active, it enters its burrow head first and the sclerotized disc fits perfectly to the walls of the tunnel, forming a false bottom that is impenetrable.

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A nice view of the peculiar disc of Cyclocosmia truncata. Author unknown. Photo taken from imgur.com

Not much more is known about the truncate trapdoor spider or its close relatives. They seem to be considerably rare, living in very restrict habitats, and their burrows are so well hidden that it is hard to find them in the wild.

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References:

Gertsch, W. J.; Platnick, N. I. (1975) A revision of the trapdoor spider genus Cyclocosmia (Aranae, Ctenizidae). American Museum Novitates 2580: 1–20.

Hunt, R. H. 1976. Notes on the ecology of Cyclocosmia truncata (Aranae, Ctenizidae) in Georgia. Journal of Arachnology 3: 83–86.

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Friday Fellow: Sharp-Toothed Venus Seed-Shrimp

by Piter Kehoma Boll

We reached again one of those problematic weeks in which I have to talk about something I know very little. This time the problem is called Euphilomedes carcharodonta, a small crustacean of the class Ostracoda, known as ostracods or seed shrimps. I decided to adapt the name of this species as sharp-toothed Venus seed-shrimp.

Although seed shrimps form a very diverse and species-rich group of organisms, I cannot find much details on particular species, so it is a challenge to present one here, but I decided to talk a little about the sharp-toothed Venus seed-shrimp, so let’s go.

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A male of the sharp-toothed Venus seed-shrimp. The dark spot is a lateral eye. Photo by Ajna Rivera.*

Measuring only a few milimeters, the sharp-toothed Venus seed-shrimp is found in the sea along the west coast of the United States. It has a typical ostracod appearance, looking like a small shrimp within a bivalvian shell.

Males and females of the sharp-toothed Venus seed-shrimp show sexual dimorphism, part of which is not only related directly to sex, but actually to the different niches that each sex occupies in the environment. Females pass most of their time buried in the sediments where light and predators are limited and, as a result, they have poorly developed eyes. The males, on the other hand, spend a lot of their time swimming in the water and are very vulnerable to predators, such as fish. Therefore, males have very well developed eyes that allow them to see fish from the distance. Experiments have shown that the eyes do not help them to identify the tiny females, but are essential to survive predation.

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A female sharp-toothed Venus seed-shrimp. Notice how she does not have the lateral eye seen on the male. Photo by Ajna Rivera.*

And that’s what I got about this fellow. As I asked before while talking about other groups of organisms, such as foraminiferans, if you have good resources on more detailed knowledge about species in this group, please share them in the comments. We need to give more visibility to those tiny and neglected souls that share this planet with us.

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References:

Sajuthi, A., Carrillo-Zazuetta, B., Hu, B., Wang, A., Brodnansky, L., Mayberry, J., & Rivera, A. S. (2015). Sexually dimorphic gene expression in the lateral eyes of Euphilomedes carcharodonta (Ostracoda, Pancrustacea) EvoDevo, 6 : 10.1186/s13227-015-0026-2

Speiser, D. I., Lampe, R. I., Lovdahl, V. R., Carrillo-Zazueta, B., Rivera, A. S., & Oakley, T. H. (2013). Evasion of Predators Contributes to the Maintenance of Male Eyes in Sexually Dimorphic Euphilomedes Ostracods (Crustacea) ntegrative and Comparative Biology, 53 (1), 78-88

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Friday Fellow: Crescent-Cup Liverwort

by Piter Kehoma Boll

Today’s fellow is once more a small forest dweller, more precisely a liverwort. Scientifically called Lunularia cruciata, its common name is crescent-cup liverwort. The names Lunularia and crescent-cup come from the shape of its cups, structures that contain mass of cells called gemmae that are released in the environment and  can grow into a new plant, a form of asexual reproduction.

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This close up of a crescent-cup liverwort reveals the crescent-shaped cups containing the gemmae. Credits to BioImages – the Virtual Fieldguide (UK).*

The crescent-cup liverwort appears to be native from Southern Europe, around the Mediterranean, but in the last decades, possibily due to human interference, it has expanded its distribution to the north of Europe and has reached other continents as well, especially the Americas.

In the United States, the crescent-cup liverwort has become a very common species living in green houses. Its quick spread is certainly related to its asexual reproduction. The gemmae found in its cups are usually released by water drops and germinate as soon as they fall on a humid surface, quickly originating a new plant.

Although most populations seem to reproduce only asexually, sexual reproduction occurs as well and follows the basic pattern seen in other liverworts. In sexual populations, the female gametophytes produce a long stem with four archegonia (the structure that bears the female gametes) arranged as a cross, hence the specific epithet cruciata (“crossed”).

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The cross-shaped archegonia of the crescent-cup liverwort. Photo by Ken-ichi Ueda.**

Some extracts from the crescent-cup liverwort has shown the potential to be used for the development of new antibiotics.

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References:

Basile, A., Giordano, S., Sorbo, S., Vuotto, M. L., Ielpo, M T. L. & Cobianchi, R. C. (1998). Antibiotic Effects of Lunularia cruciata (Bryophyta) Extract Pharmaceutical Biology, 36 (1), 25-28 : 10.1076/phbi.36.1.25.4612

Wikipedia. Lunularia. Available at < https://en.wikipedia.org/wiki/Lunularia >. Access on May 26, 2018.

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Friday Fellow: Common Pelomyxa

by Piter Kehoma Boll

It’s time to dig deep into the mud again and bring up a peculiar protist, the third species of the clade Amoebozoa to be featured here. Its binomial name is Pelomyxa palustris, and I decided to call it the common pelomyxa.

Measuring up to 5 mm in length, although usually having less than 1 mm, the common pelomyxa is considered a “giant amoeba”. In fact, the Giant Amoeba Chaos carolinense, previously featured here, was once classified in the genus Pelomyxa, but currently we know that they are not closely related at all. While the true giant amoebas of the genus Chaos are closely related to the common amoebas of the genus Amoeba, the species in Pelomyxa belong to a completely different group of amoebas.

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A specimen of the common pelomyxa. The large pseudopod is to the right and the small uroid can be seen projecting from the cell at the upper left. Credits to Proyecto Agua.*

The cell of the common pelomyxa has a somewhat cylindrical shape with a single, large, semicircular pseudopod at the front, thus moving basically always in the same direction, forward, differently from the more classical amoebas with several pseudopods and the ability to move in any direction. At the opposite side of the cell, the common pelomyxa has a small, also semicircular appendix called the uroid that is covered by several small non-motile flagella. The flagella are surrounded by small cytoplasmic projections (villi) that are easily seen under the microscope.

The common pelomyxa lives buried in the sediments of freshwater lakes throughout the northern hemisphere, especially those rich in decaying organic matter. It slides through the mud while feeding on smaller microorganisms and organic debris. Such an environment is characterized by the complete absence or extremely low concentrations of oxygen. As a result, the common pelomyxa is anaerobic and even lacks mitochondria. For this reason, it was once considered part of a very primitive group of eukaryotes that diverged before the incorporation of the endosymbiotic bacteria that would evolve into mitochondria. Currently, however, it is known that their lack of mitochondria is actually due to a secondary loss and they seem to be related to true amoebas and slime molds.

More than only lacking mitochondria, the cell of the common pelomyxa has a lot of peculiar features. Depending on the size of the cell, it may contain a few to several hundred nuclei. The cytoplasm also appears to lack several typical eukaryotic organelles, such as the Golgi apparatus and the endoplasmic reticulum. There are, however, many, many small vacuoles, so many that the cell usually has a foamy appearance.

Endosymbiotic bacteria are also found in great numbers in the cytoplasm of the common pelomyxa. After several years of research, it seems that these bacteria are obligate symbionts. Perhaps they help this strange amoeba to perform some of the tasks that should be done by the several organelles that it lacks.

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References:

Goodkov, A. V.; Chistyakova, L. V.; Seravin, L. N.; Frolov, A. O. (2004) The concept of pelobionts (Class Peloflagellatea): Brief history and current stateEntomological Review 84(Suppl. 2): S10–S20.

Wikipedia. Pelomyxa. Available at < https://en.wikipedia.org/wiki/Pelomyxa >. Access on May 26, 2018.

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Friday Fellow: Cosmopolitan Springtail

by Piter Kehoma Boll

Many very small creatures live everywhere, yet we don’t even know that they are there, and even the few of us who do know still know very little about them. One of those creatures is Entomobrya nivalis, commonly known as the cosmopolitan springtail. The fact that it has a common name, however, does not make it a very well studied species, unfortunately.

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A specimen of the cosmopolitan springtail in Norway. Credits to Biopix.*

As the common name implies, the cosmopolitan springtail is found all round the world, although it is much more common in the Northern Hemisphere, especially in Europe. Measuring about 2 mm in length, it has an average size for a springtail.

The natural habitat of this little creature are forests, and it may be found both in the leaf litter and on trees. Usually, the first instars, the juveniles, live in the leaf litter, where adults lay their eggs. During summer, adults migrate upward on the trees and live among lichens growing on the branches, a habitat that they seem to consider very cozy.

When winter approaches, and with it the freezing temperatures, the cosmopolitan springtail seeks shelter under lose portions of the bark. This shelter, however, is not enough to protect it from temperatures that would make it freeze to death. As a result, its hemolymph (“blood”) is full of antifreeze compounds that allow it to withstand temperatures as low as -18°C before freezing.

It is a small but tough guy.

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References:

Meier, P.; Zettel, J. (1997) Cold hardiness in Entomobrya nivalis (Collembola, Entomobryidae): annual cycle of polyols and antifreeze proteins, and antifreeze triggering by temperature and photoperiod. Journal of Comparative Physiology B167(4): 297–304. https://doi.org/10.1007/s003600050077

Joosse-van Damme, E. N. G. (1965) Pitfall-trapping as a method for studying surface dwelling collembolaZeitschrift für Morphologie und Ökologie der Tiere55(5): 587–596.

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Friday Fellow: Handsome Asterisk-Diatom

by Piter Kehoma Boll

It’s time for the next diatom to be featured here. Differently from the previous ones, today’s diatom is a freshwater species commonly found in lakes of North America and Eurasia. It has also been reported for South America and Africa, but it is likely that these individuals actually belong to another, closely related species.

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Asterionella formosa from a lake of the Rocky Mountain National Park, United States

Named Asterionella formosa, this diatom has small rod-shaped cells that are 60 to 85 µm long and only 2 to 4 µm wide. The individuals usually organize themselves in colonies linked by one of the ends in a star fashion. Most colonies include eight organisms and look somewhat like an asterisk, hence I chose to give the common name asterisk-diatom to the genus, this species then being called the “handsome asterisk-diatom”, from the translation of the specific epithet formosa. However, some colonies may have up to 20 individuals and organize in a more spiral fashion.

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A spiral-shaped colony from a small lake in Spain. Credits to Proyecto Agua.*

Originally found and described from water supplies used in London, the handsome asterisk-diatom has a preference for cold waters, occurring commonly in temperate lakes under temperatures between 0 and 15 °C. During summer, when temperatures get too high and the light intensity also increases, its photosynthesis is inhibited by these two factors as well as by the increase in oxygen caused by the metabolism of the species itself as well of other algae from the phytoplanktonic community.

Sexual reproduction is not well known in the handsome asterisk-diatom, but must certainly occur, as asexual reproduction alone leads to a continuous decrease in cell size in all diatoms. Studies on genetic diversity show that this species is very genetically diverse, which proves that sexual reproduction indeed occurs and in a apparently high rate, contributing for the dominance of this species in many of the ecosystems of which it takes part.

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References:

AlgaeBase. Asterionella formosa Hassall. Available at < http://www.algaebase.org/search/species/detail/?species_id=31441 >. Access on May 25, 2018.

Belay, A.; Fogg, G. E. (1978) Photoinhibition of photosynthesis in Asterionella formosa (Bacillariophyceae). Journal of Phycology14(3): 341–347. https://doi.org/10.1111/j.1529-8817.1978.tb00310.x

De Bruin, A.; Ibelings, B. W.; Rijkeboer, M.; Brehm, M.; Van Donk, E. (2004) Genetic variation in Asterionella formosa (Bacillariophyceae): is it linked to frequent epidemics of host-specific parasitic fungi? Journal of Phycology40(5): 823–830. https://doi.org/10.1111/j.1529-8817.2004.04006.x

EOL – Enclyclopedia of Life. Asterionella formosa. Available at < http://eol.org/pages/917771/details >. Access on May 25, 2018.

Lund, J. W. G. (1950) Studies on Asterionella formosa Hass: II. Nutrient depletion and the spring maximum. Journal of Ecology38(1): 15–35.

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Friday Fellow: Blue Coral

by Piter Kehoma Boll

Sorry, guys! It has been about three weeks since my last post, but I was too busy with a lot of personal and academic stuff and wasn’t able to dedicate any time to the blog, but I’m back!

Let’s return with a marine animal as today’s Friday Fellow, the called blue coral, Heliopora coerulea.

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A colony of the blue coral in Thailand. Credits to Chaloklum Diving.*

Found in tropical waters of the Pacific and Indian oceans, the blue coral is a peculiar species, being the only one in the genus Heliopora and in the family Helioporidae. It is the only species in the subclass Octocorallia that has a massive skeleton, a feature more common in the stony corals of the subclass Hexacorallia. As a result, the ecological role of the blue coral is usually closer to that of stony corals that to that of its closer relatives.

The skeleton of the blue coral is composed of aragonite and has a distinctive bluish-gray color caused by the presence of iron salts. There are fossils of bluish corals with the same morphology that date back to the Cretaceous, indicating that this is a very old species.

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A skeleton of the blue coral in the Natural History Museum, London. Photo by Wikimedia user Kinkreet.**

Although widespread, the blue coral is currently considered a vulnerable species, with some population showing very low genetic diversity. This species is threatened mainly by the jewelry and aquarium trades and by the acidification of the oceans.

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References:

Babcock, R. (1990) Reproduction and development of the blue coral Heliopora coerulea (Alcyonaria: Coenothecalia)Marine Biology 104: 475–481.

EOL: Encyclopedia of Life. Heliopora coerulea. Available at < http://eol.org/pages/1006937/overview >. Access on May 14, 2018.

Wikipedia. Heliopora coerulea. Available at < https://en.wikipedia.org/wiki/Blue_coral >. Access on May 14, 2018.

Yasuda, N.; Taquet, C.; Nagai, S.; Fortes, M.; Fan, T.-Y.; Phongsuwan, N.; Nadaoka, K. (2014) Genetic structure and cryptic speciation in the threatened reef-building coral Heliopora coerulea along Kuroshio Current. Bulletin of Marine Science 90(1): 233–255. https://doi.org/10.5343/bms.2012.1105

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