Friday Fellow: Common Silent Bell

by Piter Kehoma Boll

Among the numerous groups of single-celled organisms, the ones that seem to be the closest to the animals are the choanoflagellates. Since none had been presented here yet, let’s introduce one today. Named Codosiga botrytis, I decided to call it the common silent bell. Silent bell here is a translation of the genus name, Codosiga, which comes from Greek kodon, bell and sigē, silence, whisper.

A small colony of Codosiga botrytis in Spain. Credits to Proyecto Agua.**

Found in freshwater, especially in Europe, the common silent bell has the typical appearance of most choanoflagellates. Its cell is oval and has a single flagellum that comes out of its posterior end. Around the base of the flagellum, there is a type of collar formed by many finger-like projections. This makes the cell look kind of like a bell indeed.

While many choanoflagellates swim freely as isolated cells, the common silent bell forms colonies of cells that are attached, through a small stalk at their anterior end, to a larger main stalk that is, in turn, attached to the substrate. The number of cells in a colony varies and increases as the cells reproduce asexually, reaching a maximum of about 20 cells.

A slightly larger colony. Credits to micro*scope.*

By moving their flagella, the cells generate a water current that moves upward along the colony and allows them to capture small particules with their colar and ingest them. Most of those particles are bacteria, but other organic particles, perhaps even viruses, can also be present in their diet.

Despite being a considerably common species and a considerable number of studies having focused on the ultrastructure of its cells, little is known about the ecology and physiology of the common silent bell. For example, no one knows how and if it reproduces sexually. Actually, we do not know anything about the sexual reproduction of any choanoflagellate, but there is genetic evidence suggesting that they can, indeed, reproduce sexually. We just need to investigate them more because, as with many other little investigated species, they probably hide interesting secrets.

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References:

Carr, M., Leadbeater, B. S., & Baldauf, S. L. (2010). Conserved meiotic genes point to sex in the choanoflagellates. Journal of Eukaryotic Microbiology, 57(1), 56-62. https://doi.org/10.1111/j.1550-7408.2009.00450.x

Fenchel, T. (2019). Filter-feeding in colonial protists. Protist, 170(3), 283-286. https://doi.org/10.1016/j.protis.2019.04.002

Stoupin, D., Kiss, A. K., Arndt, H., Shatilovich, A. V., Gilichinsky, D. A., & Nitsche, F. (2012). Cryptic diversity within the choanoflagellate morphospecies complex Codosiga botrytis–Phylogeny and morphology of ancient and modern isolates. European journal of protistology, 48(4), 263-273. https://doi.org/10.1016/j.ejop.2012.01.004

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* This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

** This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic License.

Friday Fellow: Black Truffle

by Piter Kehoma Boll

Humans eat many species of fungi, most of which we call mushrooms. Although most mushrooms belong to the phylum Basidiomycota, some belong to the Ascomycota, such as the morels and the truffles, which are among the most expensive edible fungi in the world.

This is certainly the case for the black truffle, Tuber melanosporum. Native from Southern Europe, especially Spain, France, Italy and Croatia, the black truffle lives as ectomychorrhizae, i.e., a beneficial symbiont on plant roots. The plants, which include oaks, hazels, cherry trees and others, benefit from the association with the truffles by improving their rooth growth and photosynthesis, for example. This occurs because the truffles provide the plants with many important nutrients, such as potassium, phosphorus, nitrogen, sulfur, iron, copper and many others. In turn, the plant provides carbon to the truffle in the form of carbohydrates.

A black truffle on the ground. Photo by Wikimedia user Royonx.*

However, for other plants living near those trees, the presence of the truffles can be a nightmare. Dedicated to ensure the dominance of its tree friend, the black truffle can parasitize the roots of nearby trees and emit volatile compounds that cause oxidative stress on other plants, limiting their growth. As a result, a ring deprived of vegetation can be seen around the companion trees.

A ring deprived of vegetation around a tree associated with truffles. Photo by Marianne Casamance.***

The fruiting bodies of the black truffle grow under the ground. They are more or less round, with a dark skin with pyramidal protrusions and reach about 10 cm in diameter, although sometimes some can become much larger. The flesh is initially white but becomes dark and permeated by white lines as the fruiting body matures.

Some fruiting bodies after collection in Croatia, with one split in half to show the color of the flesh. Photo by John Plischke.*

One of the most striking characteristics of the fruiting bodies is their strong aromatic smell, which is caused by a mix of several volatile compounds, including alcohols, aldehydes and sulfur compounds, many of which are also present in the aroma of several vegetables or in the pheromones of certain animals. Part of these compounds are produced by the truffle itself and others by yeasts that live associated with it.

This strong smell has its ecological function, of course. It can attract species that feed on the fruiting bodies, such as pigs, which dig up the fruiting bodies and help spread the spores. Flies of the genus Suilla are also attracted by the smell and lay their eggs above the fruiting bodies, so that their larvae can feed on them.

Humans have also developed a taste for those aromatic fruiting bodies and have been eating them for centuries or even millenia. Due to the pigs’ interest in truffles, they are often used as a tool to detect the fruiting bodies underground. However, as pigs are interested in eating them, just like us humans are, they are always eager to dig the truffles up, which may damage not only the fruiting bodies but the mycelial networks too. Consequently, their use as truffle detector has been decreasing and dogs started to be used instead, as they can be trained to detect the fruiting bodies but are not interested in eating them. Likewise, when one finds Suilla flies flying or walking around a spot over the ground, it most likely means that there is a truffle there.

A dog looking for truffles. Photo by Wikimedia user Classicalordinal.*

Although highly appreciated by humans, black truffles are very expensive, with a price that can reach 2 thousand euros per kg. As a result, they are not that frequently consumed. Their aroma fades aways very quickly when they are heated, so they are usually eaten raw, especially as thin slices placed over other food.

Slices of black truffle over pasta. Photo by Sarah Stierch.*

Currently, black truffles are cultivated in several regions around the world, including the United Kindgom, Australia, New Zeland, South Africa and North and South America. On the other hand, climate change is threatening the populations in forests of its native regions in southern Europe.

Have you ever eaten truffles? What do they taste like?

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References:

Kohler, A., Kuo, A., Nagy, L. G., Morin, E., Barry, K. W., Buscot, F., … & Martin, F. (2015). Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists. Nature genetics, 47(4), 410-415. https://www.nature.com/articles/ng.3223

Le Tacon, F., Rubini, A., Murat, C., Riccioni, C., Robin, C., Belfiori, B., … & Paolocci, F. (2016). Certainties and uncertainties about the life cycle of the Périgord black truffle (Tuber melanosporum Vittad.). Annals of Forest Science, 73(1), 105-117. https://annforsci.biomedcentral.com/articles/10.1007/s13595-015-0461-1

Wikipedia. Tuber melanosporum. Available at < https://en.wikipedia.org/wiki/Tuber_melanosporum >. Access on 25 March 2022.

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* This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

** This work is licensed under a Creative Commons Attribution 4.0 International License.

** This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Friday Fellow: Common Scorpionfly

by Piter Kehoma Boll

Scorpionflies (Mecoptera) make up an important but not very popular insect order. The most known and studied species is the common scorpionfly (Panorpa communis), which is native to Europe and northern Asia.

Male with his scorpion-like tail. Photo by Charles J. Sharp.*

Adults of this species can be found during late spring and summer, between May and September. They measure about 3 cm in length and have two pairs of transparent wings with some dark spots. The body is yellow and black. Males have a pair of claspers at the end of the tail, which is curved upwards and used to hold the female during mating. This feature, found only in males, is what gives these creatures the common name of scorpionfly.

A female with her non-scorpion-like tail. Photo by Zeynel Cebebi.*

Common scorpionflies are carnivores and feed on other insects, especially dead ones. They often steal insects from spider webs, but can also capture live ones on the surface of the plants where they live, especially aphids, which are often just sitting there sucking sap.

A pair of common scorpionflies mating. Notice the male grapsing the female’s tail. Photo by Gabriel Buissart.**

When the common scorpionflies mate, the male grasps the female’s abdomen with his claspers to keep them connected. A single female mates with multiple males and stores their sperm in a storage organ until fertilization. The female lays the eggs in the soil, especially near waterbodies to keep them moist. The eggs absorb water from the environment and increase in size. The larvae look like small caterpillars, having the same sclerotized head and false legs as true caterpillars. They live on the soil, feed on plant matter and dead animals, and pupate in the soil as well.

I did not find any photo of a larva of the common scorpionfly. Here is a larva of the Japanese scorpionfly, Panorpa japonica. Photo by Ryosuke Kuwahara.***

The common scorpionfly shares the same area with a closely related species, the meadow scorpionfly (Panorpa vulgaris). Both species are very similar and have the same diet, i.e., dead arthropods. The main difference is that the common scorpionfly prefers to scavenge in shaded areas and the meadow scorpionfly in open, sunny areas. Thus, they kind of avoid confrontation and direct competition for resources, although they are more common and easily located in open areas, which makes the meadow scorpionfly somehow more successful. However, as the common scorpionfly explores areas that the meadow scorpionfly dislikes, both end up in harmony. However, as deforestation and global temperatures increase, the habitats adequate for the common scorpionfly start to decrease, threatening its persistence.

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References:

Sauer, K. P., Vermeulen, A., & Aumann, N. (2003). Temperature‐dependent competition hierarchy: a mechanism stabilizing the phenological strategy in the scorpionfly Panorpa communis L. Journal of Zoological Systematics and Evolutionary Research, 41(2), 109-117. https://doi.org/10.1046/j.1439-0469.2003.00206.x

Siegmund, B. W. (2007). Sperm competition in the scorpionfly Panorpa communis (Mecoptera, Insecta). https://hdl.handle.net/20.500.11811/3045

Wikipedia. Panorpa communis. Available at < https://en.wikipedia.org/wiki/Panorpa_communis >. Access on 24 February 2022.

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* This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

** This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

*** This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Friday Fellow: Virginia Acorn Worm

by Piter Kehoma Boll

Hidden in the bottom of the sea and feeding on dirt are some creatures that are fundamental to our understanding of animal evolution. One of these creatures is Saccoglossus kowalevskii, also known as the Virginia acorn worm.

The acorn worms (class Enteropneusta) are worm-shaped animals in the phylum Hemichordata, which is closely related to echinoderms and chordates, more to the former than to the latter. Their body consists of three parts: the proboscis, the collar and the trunk. The proboscis is an anterior portion that in some species is acorn-shaped, hence the name acorn worms; it is highly muscular, contains the heart and the kidney and is used to capture food. The collar is a short ring-like region where the mouth is located and the trunk forms the largest and longest part of the body and contains the rest of the organs.

The proboscis, the collar and the trunk can be clearly distinguished in this collected specimen. Photo by Mike Gigliotti.**

The Virginia acorn worm is found near the Atlantic coasts of North America and Europe but is rarely seen by humans. Measuring up to 15 cm in length, it lives in U-shaped burrows that it digs in the sand. The proboscis sticks out of one of the openings and drags organic matter toward the mouth; the Virginia acorn worm is, therefore, a deposit feeder. The other opening of the burrow is used to poop. Feces are expelled as small pellets of compacted sediments.

Two buried Virginia acorn worms with their proboscis sticking out of the sediments. Photo by Zihao Wang.*

The Virginia acorn worm shows a moderate capacity for regenerating missing parts. If cut into two parts, only that contains the anterior part of the trunk is able to regenerate. Parts with only the proboscis and collar or only the posterior part of the trunk cannot recover.

Reproduction occurs through external fertilization. Females deposit a clutch of eggs embedded in a gelatinous mucous and males release their sperm over the eggs. Later, the water current separates the egg mass, scattering the eggs through the environment, where they eventually hatch into small versions of the adults. Although some acorn worms have a larval stage, in the Virginia acorn worm the development is direct.

During the past decades, the Virginia acorn worm has become an important model organism. Researchers have been studying its gene expressions and embryonic development to better understand the evolution of deuterostomes and the relationships between the nervous systems of deuterostomes and protostomes. Nevertheless, despite the considerable progress in our understanding of the embryology and gene expression of this acorn worm, little is known about its ecology and the same can be said about acorn worms in general.

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References:

Aronowicz, J., & Lowe, C. J. (2006). Hox gene expression in the hemichordate Saccoglossus kowalevskii and the evolution of deuterostome nervous systems. Integrative and Comparative Biology, 46(6), 890-901.  https://doi.org/10.1093/icb/icl045

Kaul-Strehlow, S., & Stach, T. (2013). A detailed description of the development of the hemichordate Saccoglossus kowalevskii using SEM, TEM, Histology and 3D-reconstructions. Frontiers in zoology, 10(1), 1-31. https://doi.org/10.1186/1742-9994-10-53

Lowe, C. J. (2008). Molecular genetic insights into deuterostome evolution from the direct-developing hemichordate Saccoglossus kowalevskii. Philosophical Transactions of the Royal Society B: Biological Sciences, 363(1496), 1569-1578. https://doi.org/10.1098/rstb.2007.2247

Tweedell, K. S. (1961). Regeneration of the enteropneust, Saccoglossus kowalevskii. The Biological Bulletin, 120(1), 118-127. https://doi.org/10.2307/1539342

Wikipedia. Acorn worm. Available at <https://en.wikipedia.org/wiki/Acorn_worm>. Access on 17 February 2022.

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* This work is licensed under a Creative Commons Attribution 4.0 International License.

** This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Two new potentially invasive hammerhead flatworms join the team during the pandemic

by Piter Kehoma Boll

Hammerhead flatworms form a fascinating group of land planarians that is native to Madagascar and South and Southeast Asia. Despite their huge diversity in these places, most of what we know about them comes from a few species that have been inadvertently spread to new areas.

Now, two new species join this traveling team through a new study published in the open-access journal PeerJ by a team led by Professor Jean-Lou Justine from the Muséum National d’Histoire Naturelle, Paris.

The shiny black Humbertium covidum. Photo by Pierre Gros*.

The first new species is a completely black hammerhead flatworm that was found in the Pyrénées-Atlantiques (France) and in Veneto (Italy). It was named Humbertium covidum because the study was completed during the lockdown caused by the COVID-19 pandemic and as a homage to the victims of the disease. Genetic analyses of its intestinal contents indicate that it feeds on small snails.

The greenish blue color of Diversibipalium mayottensis. Photo by Laurent Charles.*

The second new species has a beautiful blue-green iridescence over its brown color and was found in Mayotte, a French island in the Mozambique Channel between Africa and Madagascar. It was, therefore, adequately named Diversibipalium mayottensis. Due to Mayotte’s proximity to Madagascar, this larger Island, where hammerhead flatworms are native, could be its place of origin. Another interesting aspect of this species is that it forms a sister group with the other hammerhead flatworms of which we have molecular data. This could mean it forms a lineage that diverged from most hammerhead flatworms long ago.

The researchers sequenced the complete mitochondrial genome (mitogenome) of the two new species and of three other already known invasive hammerhead flatworms. This allowed the research team to present the first robust phylogeny of these planarians.

Now we have to keep going and study more hammerhead flatworms to get to known their history and dive deep into their diversity. What do you think about joining us planariologists?

The complete mitogenome of the two new hammerhead flatworms. Credits to Justine et al. (2022).*

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Reference:

Justine JL, Gastineau R, Gros P, Gey D, Ruzzier E, Charles L, Winsor L (2022) Hammerhead flatworms (Platyhelminthes, Geoplanidae, Bipaliinae): mitochondrial genomes and description of two new species from France, Italy, and Mayotte. PeerJ. http://dx.doi.org/10.7717/peerj.12725

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* This work is licensed under a Creative Commons Attribution 4.0 International License.

Friday Fellow: Jamaican Seed Shrimp

by Piter Kehoma Boll

Ostracods, or seed shrimps, are very small and very abundant crustaceans, but also very neglected by biologists. I had presented three species here before, including a bioluminescent one, and it is time for the next one. Today’s species is named Chlamydotheca spinosa and I decided to give it the common name Jamaican Seed Shrimp.

As the common name suggests, the Jamaican seed shrimp occurs in Jamaica, but it can also be found in several other Caribbean islands and in Central and South America. It is a freshwater seed shrimp and one of the largest freshwater seed shrimps with more than 6 mm in length. As in all seed shrimps, its body is covered by two shells. The shells are elongate and narrow, with a small point at the back, and bluish green marks on them.

A preserved specimen with faded colors. Extracted from Schmidt et al. (2018).*

Living at the bottom of freshwater ponds, the Jamaican seed shrimp is probably a deposit feeder, ingesting organic matter and smaller organisms, such as algae. It can be raised in aquaria very easily, which would make it a very good model for studies, only that no one seems to care. Another interesting thing about this species is the fact that it is parthenogenetic, which means females produce offspring from unfertilized eggs so that males do not exist.

Like all arthropods, the Jamaican seed shrimp molts as it grows. Its weight doubles at each molt, except for the last molt, between the eighth instar and the adult form, when it increases a little bit more, probably because of the development of the gonads.

And that’s all I could find about this little fellow. If you work with ostracods, try to provide more information about them online. That would be very useful to help us spread knowledge and love for these amazing animals.

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More ostracods:

Friday Fellow: Sharp-Toothed Venus Seed-Shrimp (on 22 June 2018)

Friday Fellow: Stonewort Seed Shrimp (on 19 July 2019)

Friday Fellow: Japanese Sea Firefly (on 27 March 2020)

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References:

Kesling, R. V., & Crafts, F. C. (1962). Ontogenetic increase in Archimedean weight of the ostracod Chlamydotheca unispinosa (Baird). American Midland Naturalist, 149-153. https://www.jstor.org/stable/2422641

Schmidt, R. E., Shoobs, N. F., & McMullin, E. R. (2018). Occurrence of the large ostracod, Chlamydotheca unispinosa (Baird, 1862), in temporary waters of Montserrat, Lesser Antilles. ZooKeys, (748), 89. https://doi.org/10.3897/zookeys.748.22323

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* This work is licensed under a Creative Commons Attribution 4.0 International License.

Friday Fellow: Human Chlamydia

by Piter Kehoma Boll

It’s time for another bacterium and why not one that loves us even though we hate it? Chlamydia trichomatis is today’s fellow, that little annoying bacterium that infects us humans and sometimes can cause us some serious problems.

The human chlamydia belongs to a phylum of bacteria known as Chlamydiae, which is simply the plural of the bacterium’s name. All Chlamydiae seem to be obligate endosymbionts of eukaryotic cells, either as parasites or in a mutualistic relationship. The human chlamydia, of course, is of the first type. This species is an exclusive parasite of humans and apparently cannot infect the cells of any other species.

The life cycle of the human chlamydia is similar to that of other chlamydia species. It has two distinct forms known as elementary bodies and reticulate bodies. The elementary bodies are a spore-like form measuring from 200 to 400 nanometers in diameter. They have a very rigid cell wall and are able to survive outside of a host cell. When an elementary body contacts a human host cell, mostly cells from the mucous membranes, it causes the host cell to make a vacuole in which it remains. This vacuole is known as an inclusion.

Chlamydia inclusions (the large bubbles in the central cell) as seen under the microscope.

Within the inclusion, the elementary body changes into the metabolically active reticulate body, which measures between 600 and 1500 nanometers. The reticulate body is capable to change the inclusion into a more suitable environment and starts to replicate very rapidly until filling the host cell with bacteria in up to 72 hours. At this point, the reticulate bodies change back to elementary bodies and make the host cell burst and release them, where they can spread to other cells and infect them as well.

The human chlamydia can infect many parts of the human body, but the most commonly affected areas are the urethra and the vagina and its transmission between humans occurs mainly through sexual intercourse as the infected person can have elementary bodies in its fluids, such as sperm and vaginal fluid. In fact, chlamydia is the most common sexually transmitted infection worldwide, with about 4.2% of all women and about 2.7% of all men having it.

Many cases of chlamydia infection can go undiagnosed because sometimes the infection does not cause any symptoms or they take a long time to appear. When it infects the vagina and cervix, symptoms are rare at first but as the infection spreads it can infect the rest of the reproductive system and cause pelvic inflammatory disease, which may lead to sterility. Some of the rare symptoms in a vaginal infection are pain during intercourse and vaginal bleeding. In the urethra, symptoms are more common and include pain or a burning sensation during urination and eventually an unusual discharge from the penis. The symptoms are very similar to those of gonorrhea.

Besides the urogenital tract, the human chlamydia can infect many other sites, such as the rectum and the oral cavity through anal and oral sex, respectively. Another commonly infected area are the eyes, with 19% of all cases of conjunctivitis being caused by the human chlamydia. If not adequately treated, this conjunctivitis evolves into a chronic condition known as trachoma that often leads to blindness. The eyes become infected by direct contact of infected hands or objects (such as towels) with the eyes. The bacterium can also be transmitted by flies as they move around human bodies licking their fluids.

Chlamydia infection by age and sex in the United States.

Chlamydia is often treated by antibiotics such as azithromycin. Prevention includes adequate hygiene, safe sexual practices and regular testing in sexually active humans since identifying the infection earlier can reduce its damage and prevent its spread to others. In the past decade, there has been an increased interest in developing a vaccine against chlamydia. One problem is the fact that the immune response against this bacterium seems to be very complex. However, preliminary tests with a candidate vaccine has led to promising results, so there is hope!

Despite being a pain in the ass (or most commonly in the crotch) for humans, the human chlamydia is at the same time a fascinating organism just like every other lifeform on Earth. It has a considerably small genome, with only bout 900 genes. Many essential metabolic genes are lacking and it is believed that they are scavenged from the host.

A human-specific parasite, the human chlamydia is believed to have become a separate lineage from other chlamydia species about 9 million years ago. This means it has been with us since before we were even humans.

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References:

Brunham, R. C., & Rey-Ladino, J. (2005). Immunology of Chlamydia infection: implications for a Chlamydia trachomatis vaccine. Nature reviews immunology, 5(2), 149-161. https://doi.org/10.1038/nri1551

Manavi, K. (2006). A review on infection with Chlamydia trachomatis. Best Practice & Research Clinical Obstetrics & Gynaecology, 20(6), 941-951. https://doi.org/10.1016/j.bpobgyn.2006.06.003

Wikipedia. Chlamydia trichomatis. Available at < https://en.wikipedia.org/wiki/Chlamydia_trachomatis >. Access on 13 January 2022.

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Friday Fellow: Sea Walnut

by Piter Kehoma Boll

Comb jellies, which make up the phylum Ctenophora, are some of the most intriguing animals. Although they may look like jellyfishes at first, both groups are not closely related, as jellyfishes are cnidarians. One of the reasons why comb jellies are less popular may be simply because they are way less diverse than cnidarians. There is only about one ctenophore species for every 100 cnidarian species.

As a result, after 318 Friday Fellows, no comb jelly has been presented here yet, but this changes today. Let’s talk about Mnemiopsis leidyi, the warty comb jelly or sea walnut. Let’s stick with the second name because it sounds nicer.

The beautiful sea walnut with its iridescent colors. Photo by Bruno C. Vellutini.*

The sea walnut is native from the western Atlantic Ocean, i.e., near the coast of the Americas. With an oval-shaped, transparent and lobed body, it measures up to 12 cm in length and 2.5 cm in diameter. Like most comb jellies, the sea walnut is able to emit light by chemical reactions when stimulated in the dark. However, this is not as often observed, although most people may think they are constantly producing colorful lights forming rainbow-like rows. However, this is caused by a refracted light and not actual bioluminescence and, as a result, can only be observed when an external light source reaches the animal.

The sea walnut is carnivore and feeds on a variety of organisms, mostly from the zooplankton, such as crustaceans, eggs and larvae of fish and even other comb jellies. Its predators include fish, birds, jellyfish and larger comb jellies.

The sea walnut doesn’t look that magical when washed ashore. Photo by iNaturalist user twosandcastles.**

One interesting phenomenon in the sea walnut is its defecation. It has a sack-like gut that most of the time has only the mouth as its opening. However, when its gut is filled with feces, part of it kind of balloons out until touching the epidermis and fuses with it, forming a temporary anus through which feces are expelled. The process is reverted and the anus disappears soon after. But there is one more peculiar thing about this story. Defecation occurs at regular intervals, about once every hour in the adults and once every 10 minutes in the larvae. Can you imagine that? Having to make and unmake your anus every hour? Or every ten minutes?

Despite its bioluminescence and iridescent colors, the sea walnut has a dark side as well. As I said above, this species is native to the Western Atlantic, where it lives just fine with other sea creatures. In the 1980s, however, it was accidentally introduced in the Black Sea, probably through ballast water from merchant ships. First observed in 1982, the species reached a density of up to 400 specimens per m³ in 1989. Its presence caused a dramatic drop in the populations of an anchovy species, Engraulis encrasicholus, a commercially important fish in this region. To control its population, another comb jelly was deliberately introduced in the Black Sea, Beroe ovata, which is a natural predator of the sea walnut. Fortunately, both species seem to have reached a stable predator-prey dynamic, otherwise the situation could have become even worse.

But humans never get tired of finding new ways to ruin ecosystems, right? Russia developed a network of channels running across the country’s rivers that connect several saltwater bodies for navigation, including the Black Sea, the Caspian Sea, the Baltic Sea, and the White Sea. As a result, the sea walnut was able to spread from the Black Sea into the Caspian Sea in 1999. There, it started to feed on the eggs and larvae of small fish and led to a reduction in the population of larger fish and seals.

During the 21st century, the sea walnut continued to spread across European seas, colonizing the Mediterranean, the Baltic and the North Seas. Its impact on these areas is still unknown, but it could be catastrophic, especially in the Baltic Sea, which is one of the most impacted marine environments in Europe.

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References:

Schnitzler, C. E., Pang, K., Powers, M. L., Reitzel, A. M., Ryan, J. F., Simmons, D., … & Baxevanis, A. D. (2012). Genomic organization, evolution, and expression of photoprotein and opsin genes in Mnemiopsis leidyi: a new view of ctenophore photocytes. BMC biology, 10(1), 1-26. https://doi.org/10.1186/1741-7007-10-107

Shiganova, T. A., Sommer, U., Javidpour, J., Molinero, J. C., Malej, A., Kazmin, A. S., … & Delpy, F. (2019). Patterns of invasive ctenophore Mnemiopsis leidyi distribution and variability in different recipient environments of the Eurasian seas: A review. Marine environmental research, 152, 104791. https://doi.org/10.1016/j.marenvres.2019.104791

Wikipedia. Mnemiopsis. Available at < https://en.wikipedia.org/wiki/Mnemiopsis >. Access on 06 January 2022.

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* This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

** This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

An adventurous life did not end well for this polyclad

by Piter Kehoma Boll

Polyclads are marine flatworms, some of which have amazing colors and are often mistaken for sea slugs. Although very few freshwater species are known to exist, there are no terrestrial species (although this has been suggested by a delusional naturalist about 150 years ago).

However, in 2018, one marine polyclad seems to have decided to explore the world outside the oceans by riding a toad in Bangladesh. How did this happen? Well, no one is sure. A group of researchers working on Nijhun Dwip Island found a common Asian toad (Duttaphrynus melanosticus) walking through an agricultural field with a polyclad attached to its dorsum.

The toad and the polyclad. A new Aesop’s fable. Credits to Rabbe et al. (2020).*

A canal that passes through the field can be flooded by the sea during high tide and this is how the researchers think the flatworm ended up on land and eventually on the back of the toad. Unfortunately, because the toad was spotted by the researchers, the poor polyclad ended up collected and killed and is now preserved in a lab.

Not all adventures have happy endings…

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References:

Rabbe MF, Roy DK, Mohammad N, Liza FT, Mukutmoni M, Alam MM, Begum A & Jaman MF. 2020. A Novel Natural History Phenomenon: A Free-living Marine Flatworm (Polycladida) Attached to a Common Asian Toad (Duttaphrynus melanostictus). Reptiles & Amphibians 27: 293–294. https://journals.ku.edu/reptilesandamphibians/article/view/14404

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* This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Friday Fellow: King Fern

by Piter Kehoma Boll

Ferns make up an amazing group of plants and can have many different shapes and sizes. Some can grow like a tree, the so-called tree ferns, which are the tallest ferns in the world today. However, some other not-quite-tree ferns can also become really large. And one of those is today’s fellow, Angiopteris evecta, known as the king fern, giant fern, oriental vessel fern and many other names.

Native from Indonesia, Australia and many Pacific Islands near the equator, the king fern was discovered by European naturalists in the second half of the 18th century and it soon started to be cultivated as an ornamental plant due to its astonishing looks. The fronds (i.e., leaves) of the king fern are bipinnate, meaning that they have a feather shape, like in most ferns, where the leaflets are themselves formed by smaller leaflets. The shape of those fronds is nothing that special, but their size is amazing, as they can reach up to 9 m in length and 2.5 m in width. About 2 m of its length is formed by the thick and fleshy petiole. This makes them the largest fern leaves in the world, and they are even more incredible because despite this huge size they have no hard, woody tissues to sustain them, relying entirely on the hydraulic pressure of the sap.

The fronds of the king fern are so huge it is very hard to take a good photo of them. Credits of this one to Forest & Kim Starr.**

The rhizome (i.e., stem) of the king fern is also huge. It can reach up to 1 m in diameter and get very long. Most of it lies on the ground, like a fallen tree trunk, but the tip is often vertical and can reach up to 1.5 m in height. Overall, considering the size of the huge fronds, the plant can be up to 7 m high and 16 m wide.

The preferred habitat of the king fern are hot rainforests with very rich and drainable soils and good water availability, often near the coast. The sporangia that grow on the underside of the fronds produce a very large number of spores, which enables the king fern to spread quickly across suitable areas. As a result, it became invasive in some areas where it was introduced as an ornamental plant, such as Hawaii, Jamaica, Cuba and Costa Rica. Other regions where the king fern can potentially become invasive include most of the Caribbean and the tropical forest near the coast in Central and South America, Africa and Southeast Asia.

The thick trunk-like rhizome grows horizontally on the ground, except for its terminal part, which is pointed upward. Photo by Steve Fitzgerald.*

The king fern is traditionally used as a medicinal herb by the Dayak people in Borneo, especially to treat liver problems. The rhizome is highly toxic, but apparently can be eaten after a process to extract the toxins. Studies with extracts of the plant indicated that it has the potential for the development of drugs against HIV-1 and tuberculosis.

And there is one more interesting thing about this species. There are fossil fronds from the Carboniferous, about 300 million years old, that are basically identical to those of the king fern. This suggests that this species is insanely old, and was widespread around the whole world during that time. Later, as the eras passed, it retreated to its current native location in areas near the tropical Indo-Pacific. Now, due to human intervention, it seems that the king fern is about to dominate the whole planet again 300 million years after its last empire.

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References:

Christenhusz, M. J., & Toivonen, T. K. (2008). Giants invading the tropics: the oriental vessel fern, Angiopteris evecta (Marattiaceae). Biological Invasions, 10(8), 1215-1228. https://doi.org/10.1007/s10530-007-9197-7

Kamitakahara, H., Okayama, T., Agusta, A., Tobimatsu, Y., & Takano, T. (2019). Two‐dimensional NMR analysis of Angiopteris evecta rhizome and improved extraction method for angiopteroside. Phytochemical Analysis, 30(1), 95-100. https://doi.org/10.1002/pca.2794

Wikipedia. Angiopteris evecta. Available at < https://en.wikipedia.org/wiki/Angiopteris_evecta >. Access on 30 December 2021.

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* This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

** This work is licensed under a Creative Commons Attribution 3.0 Unported License.