Friday Fellow: Swan Lacrymaria

by Piter Kehoma Boll

Among the heterogeneous group of single-celled eukaryotes often called protists, one group that shows a striking diversity and cell complexity is that of the ciliates. Today I will present one more species in this group. The first one was presented here some years ago.

Named Lacrymaria olor, today’s species lacks a common name, but swan lacrymaria seems to be a good one. Swan here comes from the translation of its specific epithet, olor, but it is very adequate considering the species’ shape. Found in freshwater ponds, it is often near aquatic vegetation or decaying plant matter, where its food also lives.

The main part of the swan lacrymaria’s body is not that different from an average ciliate, measuring about 100 µm in length and having kind of the shape of a teardrop, hence the name of the genus Lacrymaria, from Latin lacryma, tear. But extending from the cell there is a very long “neck”, which makes the whole cell look like some sort of swan with a very very long neck.

Lacrymaria olor, a microscopic swan. Photo by Flickr user Picturepest*.

This neck projection is the most active part of the swan lacrymaria’s cell. While the drop-shaped cell body part remains considerably still and hidden, the neck screens the environment looking for food, which often consists of smaller organisms. The neck can move from one side to the other, move around obstacles and extend up to 2 mm, which is about 20 times the length of the cell. The end of the neck has the oral apparatus, through which food is ingested. A ring of long cilia surround the oral apparatus, beating furiously during the hunting behavior.

Watch this amazing video with this protist in action. Extracted from Coyle et al. (2019).

When a prey is found, the swan lacrymaria quickly captures and engulfs it in less then a second, probably injecting a paralyzing toxin in the process. Once inside the “mouth”, the prey is “swallowed”, being pushed toward the main portion of the cell, which may take several seconds.

The swan lacrymaria’s incredible neck agility seems to be related to its complex cytoskeleton in which, for example, the fibers change their orientation in the neck in relation to the body. It’s amazing to watch such a complex behavior in a single-celled organism.

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References:

Coyle, S. M., Flaum, E. M., Li, H., Krishnamurthy, D., & Prakash, M. (2019). Coupled active systems encode an emergent hunting behavior in the unicellular predator Lacrymaria olor. Current Biology29(22), 3838-3850.

Wan, K. Y. (2019). Ciliate Biology: The Graceful Hunt of a Shape-Shifting Predator. Current Biology29(22), R1174-R1176.

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

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Friday Fellow: Azores Bellflower

by Piter Kehoma Boll

Oceanic Islands are a treasure of biodiversity and include many small and endemic species. When we come to the Azores archipelago, we find one of those little treasures in the form of a small shrub, the so-called Azores bellflower. Taxonomically, the species is named Azorina vidalii, being the only species in the genus Azorina. The genera of the family Campanulaceae (bellflowers) are a mess, though, and this may eventually change.

The Azores bellflower grows in all nine islands that make up the Azores. It likes to grow near the coastline, especially in crevices of the coastal rocks or sandy slopes, but it can also colonize human structures, such as roofs and walls. It likes very exposed locations and is very tolerant to the sea breeze. Although this plant is usually a very small woody shrub with about 30 cm in height, it can grow up to 2 m.

Typical look of the plant. Photo by iNaturalist user experience.NATURE.*

Despite being found across the whole archipelago, the Azores Bellflower is considered an endangered species. There are only about a thousand adult specimens in total. One of the reasons for such a small population may be due to the lack of an efficient pollinator. The flowers are light pink or white and have a shape that suggests birds as the most likely pollinators, but there is no native bird species in the archipelago that could do this job. Several insects, including bees, wasps, flies and moths, sometimes visit the flowers and may be the current pollinators, but most probably none of them is very efficient in this job. The combination of all of them seems to be enough to keep the current population relatively stable.

The beautiful flowers of the Azores bellflower. Photo by iNaturalist user mariamadalena.*

When honeybees visit the plants, they are often more interested in the latex that the Azores bellflowers secrets. The bees look for recent wounds on the plants where latex is leaking and collect it, sometimes having difficulty leaving the plant because the latex is so sticky that the bees get partially glued to the plant. It is thought that the latex has antimicrobial properties, protecting the plant from bacterial infections, and the bees most likely explore this resource to use it as a natural antibiotic in their combs, perhaps mixing it with pollen to make propolis.

A plant with more pinkish flowers. Photo by Attila Steiner.*

The current population of the Azores bellflower is stable but very small, which is the main reason why it is considered endangered. To assure its survival in the next decades or centuries (and beyond), it is essential to preserve the rocky shores where they thrive and, of course, the diversity of pollinators, which are doing their best to bring new generations of this small Azorean jewel.

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References:

Haberle, R. C., Dang, A., Lee, T., Peñaflor, C., Cortes-Burns, H., Oestreich, A., … & Jansen, R. K. (2009). Taxonomic and biogeographic implications of a phylogenetic analysis of the Campanulaceae based on three chloroplast genes. Taxon58(3), 715-734. https://doi.org/10.1002/tax.583003

Weissmann, J. A., & Schaefer, H. (2015). Honeybees (Apis mellifera) collect latex of Azores bellflowers (Azorina vidalii, Campanulaceae). ARQUIPÉLAGO. Life and Marine Sciences32. https://repositorio.uac.pt/handle/10400.3/3906

Weissmann, J. A., & Schaefer, H. (2018). The importance of generalist pollinator complexes for endangered island endemic plants. Arquipélago-Life and Marine Sciences35, 23-40. https://repositorio.uac.pt/handle/10400.3/4861

Wikipedia. Azorina. Available at < https://en.wikipedia.org/wiki/Azorina >. Access on 29 April 2021.

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

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Friday Fellow: Fire-Ant Internal Microsporidium

by Piter Kehoma Boll

Last week we learned about the red imported fire ant and the nuisance that it presents in North America, where it was introduced almost a century ago and has turned into a threat to ecosystems and people. As chemical pesticides are often harmful to species other than the one targeted, more species-specific alternatives are often sought. One of those is biological control, which can also be problematic if incorrectly used.

Today’s species is one of those biological agents that can help control the invasion of the red imported fire ant. Named Kneallhazia solenopsae, which I decided to nickname as the fire-ant internal microsporidium, this species belongs to the division Microsporidia, which are single-celled fungi. I already presented one of them here several years ago, the flounder glugea.

The fire-ant internal microsporidium is known to infect fire ants, including the red imported fire ant. It has a very complex life cycle with several stages that is not completely understood yet.

The most serious infection occurs in queens, in which the life stage known as type 2 dikaryotic spore (Type 2 DK) infects the fat body tissue. This is a stage of the microsporidium in which the cell has two nuclei, hence the name. Other adult ants are also infected similarly. The infection spreads slowly, causing hypertrophy of the fat body tissue and, at advanced infections stages, makes this tissue be completely replaced by masses of spores, preventing the development and reproduction of the queen. However, it takes a long time for the microsporidium to cause such a serious disease. It does not mean that it is doing nothing to make things worse before that, though.

While the fat body tissue of the queen is being slowly consumed by the Type 2 DK spores, many of them turn into another stage, the octospore, so called because it occurs in a vesicle which contains eight of them. These vesicles are relatively large compared to the other stages and are thought to be the infectious stage. An injured or dead ant, which is often cannibalized by others, releases the vesicles in the environment. They need to be ingested for infection to occur, but only 4-instar larvae are able to swallow them, because all other larval stages, as well as adults, have a “filter” in their mouth that prevents them ingesting particles larger than 0.8 µm and the vesicles are larger than that.

Several vesicles with octospores and a Type 2 DK spore of the fire-ant internal microsporidium. Photo by David Williams.**

Inside the 4-instar larvae, the vesicles release the octospores, which infect the larvae and fuse, turning into another type of cell with two nuclei, the Type 1 DK spores. Those spores are only found in 4-instar larvae and pupae and are supposed to turn into Type 2 DK spores during the development into adult ants, where they can produce new octospores.

But this is not the only way the microsporidium spreads through the colony. Going back to the queens, the Type 2 DK spores also infect their ovaries and, after the queen is inseminated, they turn into another stage, the so-called megaspore. These megaspores infect the eggs and are incorporated into the embryo and pass directly to the 1-instar larvae, where they develop into Type 1 DK spores as they grow.

So the only way for an ant to become infected is if it receives the parasite directly from the queen in the egg or if it ingests the octospore vesicles as a 4-instar larva? No. And the reason is the fact that ants perform trophallaxis, which is the transfer of food from one individual to the other, i.e., the ants vomit into each other’s mouth. Thus, if an adult ant exchanges food with a 4-instar larva that has released octospores in its gut, it may end up infected as well.

That is quite a complicated life cycle, right? But it seems to be quite well tuned for the microsporidium to be a successulf parasite of fire ants. Is it an efficient biological control though? Well, I would say that it may help slowing down the spread of fire ants, but as its effects causing sterility to the queen take a long time to appear, it will not lead to the removal of the ants in areas they have invaded already.

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References:

Knell, J. D., Allen, G. E., & Hazard, E. I. (1977). Light and electron microscope study of Thelohania solenopsae n. sp.(Microsporida: Protozoa) in the red imported fire ant, Solenopsis invicta. Journal of Invertebrate Pathology29(2), 192-200. https://doi.org/10.1016/0022-2011(77)90193-8

Oi, D. H., & Williams, D. F. (2002). Impact of Thelohania solenopsae (Microsporidia: Thelohaniidae) on polygyne colonies of red imported fire ants (Hymenoptera: Formicidae). Journal of Economic Entomology95(3), 558-562. https://doi.org/10.1603/0022-0493-95.3.558

Sokolova, Y. Y., & Fuxa, J. R. (2008). Biology and life-cycle of the microsporidium Kneallhazia solenopsae Knell Allan Hazard 1977 gen. n., comb. n., from the fire ant Solenopsis invictaParasitology135(8), 903.

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

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Friday Fellow: Red Imported Fire Ant

by Piter Kehoma Boll

While most species presented here have very little available information about their ecology, today’s species is a very well researched organism because it is a worldwide threat. Its current accepted binomial name is Solenopsis invicta and its common name in English is often red imported fire ant. But why?

The red imported fire ant is native from central regions of South America, including western Brazil, northern Argentina, Paraguay, Bolivia and southeastern Peru. The workers range from about 2.5 to 6 mm in length and have a reddish brown or yellowish color, with a darker abdomen. Some colonies may have two castes of workers, a smaller and a larger one, while others have only one.

Mating occurs during the warmer months, when the typical nuptial flight of ants occur. Males die after mating and queens start to build their nest, sometimes alone, sometimes in groups. Thus, colonies can have a single or multiple queens, and in the latter case they may fight for dominance. The nests are built in the ground and the soil that is displaced to excavate the nest is often deposited around the nest entrance, forming a mound of small grains.

A typical mound at the entrance of a nest. Photo by iNaturalist user stanushhn.**

The red imported fire ant is omnivorous and mainly a scavenger, feeding especially on dead animals and sweet liquids such as nectar and honeydew, the sweet substance secreted by some insects. As a predator it may attack other insects, especially dipterans and termites, but also other arthropods, such as spiders and harvestmen, and even snails or small vertebrates. Seeds are also eventually included in their diet.

Feeding on a dead cockraoch. Photo by iNaturalist user bellumknight.**

The behavior of these ants is very complex and they are very resilient, being able to adapt to both drought and flooding conditions. For example, when the soil gets covered by water, they link together and form a ball or raft that floats.

Due to its broad diet and ability to live in several habitat types, including forests and open areas, the red imported fire ant adapts very easily to new areas, and this is exactly what happened.

The red imported fire ant arrived in the United States through the seaport of Mobile, Alabama, by cargo ship, in the 1930s or 1940s and the estimations are that about 9 to 20 unrelated queens were introduced during this time. During the next decades the colonies started to spread across the southern United States and Northern Mexico, causing serious environmental and economic damage.

A raft of floating red imported fire ants during a flood. Photo by Wikimedia user TheCoz.*

Studies have shown that many native arthropods disappear from an area when the red imported fire ants arrive. Some of them become prey of the ants and others are likely displaced by competition or because the ants remove their food source. For humans, the economic impact is mostly related to their presence in plantations, where they may remove germinating seeds. If nests are built near or under roads, pavements or buildings, the soil that is displaced can eventually damage the foundations of the structure. In human-inhabited areas they can be a nuisance because of their aggressive behavior, which makes outside activities difficult.

When threatened, fire ants react with an aggressive attack in which several workers approach the threat and sting it. Their venom is formed by a mix of many compounds and, in humans, often cause a burning sensation followed by urticaria and pustule formation. Allergic people may suffer serious and life-threatening allergic reactions.

More recently, the red imported fire ant’s invasion continued and it reached the Caribbean, China, Taiwan, Australia and New Zealand. There are also non-confirmed reports of its occurrence in India and the Philippines.

Due to this combination of factors, the red imported fire ant is one more species in the list of the top 100 invasive species in the world, just like the Giant African Snail and the New Guinea Flatworm, which I presented some weeks ago.

I have to say that I find it funny to see that their presence in gardens is a problem for outside activities in the USA. As a Brazilian I spend my whole childhood playing in a backyard full of fire ants and lost count of how many times I accidentally stepped onto a nest and ended up with my foot covered by stings. Ye goode olde times.

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References:

Ascunce, M. S., Yang, C. C., Oakey, J., Calcaterra, L., Wu, W. J., Shih, C. J., … & Shoemaker, D. (2011). Global invasion history of the fire ant Solenopsis invicta. Science331(6020), 1066-1068. https://science.sciencemag.org/content/331/6020/1066.full

Morrison, L. W. (2002). Long‐term impacts of an arthropod‐community invasion by the imported fire ant, Solenopsis invicta. Ecology83(8), 2337-2345. https://doi.org/10.1890/0012-9658(2002)083[2337:LTIOAA]2.0.CO;2

Morrison, L. W., Porter, S. D., Daniels, E., & Korzukhin, M. D. (2004). Potential global range expansion of the invasive fire ant, Solenopsis invicta. Biological invasions6(2), 183-191. https://doi.org/10.1023/B:BINV.0000022135.96042.90

Wikipedia. Red Imported Fire Ant. Available at < https://en.wikipedia.org/wiki/Red_imported_fire_ant >. Access on 15 April 2021.

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Friday Fellow: Puerto Rican Glasscup

by Piter Kehoma Boll

If you ever happen to walk in the woods, or sometimes in open spaces as well, and find a series of small often semitransparent cup-like mushrooms protruding from the soil or vegetation, you may be in front of a peculiar group of fungi, the glasscups, which make up the genus Orbilia. Today we will talk about one of these species that is found in Puerto Rico, Orbilia jesu-laurae, which I decided to call the Puerto Rican glasscup.

As most fungus, the glasscups have two life stages, a sexual and an asexual one. During the sexual stage, the Puerto Rican Glasscup produces small circular fruiting bodies measuring only about 1.5 mm in diameter with a light-brown to orange-brown color. Their margins may be somewhat undulating, disrupting the aspect of a perfect circle.

Fruiting bodies of the Puerto Rican glasscup. Extracted from Quijada et al. (2020).

When the fruiting bodies release spores in the environment, they will germinate and originate the asexual stage, which will grow in the substrate to form a network of hyphae, the mycelium, as typical of most fungi. However, while most fungi are parasites or saprotrophs during this stage, the Puerto Rican Glasscup is a predator.

Growing across the substrate, the mycelium of the Puerto Rican Glasscup looks for small nematodes, which are very common in the environment, and traps them with the hyphae. Once the nematode is trapped, the fungus will grow hyphae inside it, feeding on its tissues.

Capture of a nematode by the Puerto Rican glasscup. The nematode is near the hyphae in C1, captured by the hyphae, but still alive, in C2 to C3, and dead and filled by hyphae in C4. Photo extracted from Quijada et al. (2020).

The glasscup still feeds on decomposing plant material, though. In fact, the reason for it consuming nematodes is probably because they provide a good source of nitrogen, which may not be very available in the substrate. Thus, they act more or less like carnivorous plants.

Not all glasscups seem to be predators, but many are. Nematodes are the most common prey but some species may feed on other small animals, especially small arthropods such as copepods, collembolans, dipterans and mites. As many nematodes, and other of the eventually consumed small animals, are plant pests, it has been suggested that glasscups may be used as a biological control of these creatures, but there are no studies addressing the viability of such method yet.

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References:

Moosavi, M. R., & Zare, R. (2020). Fungi as biological control agents of plant-parasitic nematodes. In Plant defence: biological control (pp. 333-384). Springer, Cham. https://www.researchgate.net/profile/Rasoul-Zare/publication/227255809_Fungi_as_Biological_Control_Agents_of_Plant-Parasitic_Nematodes/links/09e4150b346c874d3a000000/Fungi-as-Biological-Control-Agents-of-Plant-Parasitic-Nematodes.pdf

Quijada, L., Baral, H. O., Beltrán-Tejera, E., & Pfister, D. H. (2020). Orbilia jesu-laurae (Ascomycota, Orbiliomycetes), a new species of neotropical nematode-trapping fungus from Puerto Rico, supported by morphology and molecular phylogenetics. Willdenowia50(2), 241-251. https://doi.org/10.3372/wi.50.50210

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Friday Fellow: Broadlef Sea Lettuce

by Piter Kehoma Boll

If you are used to go to the beach, especially rocky shores, you my have seen some small green “leafy” things growing on the rocks and sometimes washed ashore that look like small lettuce plants or something like that. Well, those are green algae of the species Ulva lactuca, commonly known as sea lettuce. However, as this name is also used for other species of Ulva, the name broadleaf sea lettuce is sometimes used to refer to this specific species.

Broadlef sea lettuce growing around Sand Diego, USA. Photo by iNaturalist user annegero-stillwell.*

The thallus of the broadleaf sea lettuce is very thin and semitransparent, being only two cells thick. It often has a ruffled or torn margin and can grow up to 18 cm in length and 30 cm in width, but it is normally much smaller. It is attached to the substrate, often rocks, but sometimes other organisms, by a small disc-shaped holdfast.

As all plants, the broadleaf sea lettuce has a haploid phase (in which cells has only one chromosome of each) and a diploid phase (with two chromosomes of each per cell). Both phases have the same overall appearance, but the haploid plants are either male or female and release gametes into the water, which join to form a zygote, which will grow to form a diploid plant. This, in turn, releases movable spores (zoospores), which will germinate to produce new haploid plants.

A specimen in northern France. Photo by iNaturalist user simondenis142857.*

The broadleaf sea lettuce has a worldwide distribution, being found in all continents and oceans. It is an edible alga and is particularly rich in iron and the amino acid histidine. However, one must have caution about where it is harvested for consumption, as it can accumulate heavy metals in polluted zones.

Specimen from Rio de Janeiro, Brazil. Yummy, isn’t it? Photo by Ricardo da Silva Ribeiro.*

In nutrient-rich waters due to pollution, the populations of the broadleaf sea lettuce can grow very quickly and thousands of individuals may end up washed ashore. When they start to decompose, they emit toxic gases such as hydrogen sulfide, which may kill animals by hypoxia, i.e., lack of oxygen, as it inhibits cellular respiration. There are records of humans dying after walking near large amounts of decomposing algae.

Lifeforms often have this dual nature, and the same thing that can make you stronger can also kill you.

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References:

Dominguez, H., & Loret, E. P. (2019). Ulva lactuca, a source of troubles and potential riches. Marine drugs17(6), 357. https://doi.org/10.3390/md17060357

Wikipedia. Ulva lactuca. Available at < https://en.wikipedia.org/wiki/Ulva_lactuca >. Access on 1 April 2021.

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Friday Fellow: Hawaiian Purple Bryozoan

by Piter Kehoma Boll

Beauty itself is often not enough to prompt invertebrate research, either through the researchers themselves or the ones founding their research. This seems to be the case with today’s fellow, an absolutely beautiful but completely unstudied bryozoan, Disporella violacea, which I decided to call the Hawaiian purple bryozoan.

This is an encrusting species of bryozoan, meaning it grows firmly attached to the substrate, which can be rocks or the surface of other species with a hard skeleton, such as mollusks, especially bivalvians. It is colonial, of course, which is the rule for bryozoans, and the individual zooids are often organized circularly. The whole colony has a beautiful purple or blue tinge and appears as a flat, often irregular, purple spot with many lighter circular marks formed by the circularly-organized zooids.

Disporella violacea around Oahu, Hawaii. Photo by Craig Fujii.*

I have found a single source stating that the Hawaiian purple bryozoan is found across the Indo-Pacific, but I was only able to find photographs of colonies growing in coral reefs around Oahu in Hawaii.

What can we say about its ecology? Well, nothing. I could not find a single paper dealing with this species. We have no idea how it interacts with other species, how it reproduces, nothing! It belongs to the order Cyclostomatida, often called the cyclostomes (not to mistake for the Cyclostomata, which includes lampreys and hagfish). Cyclostome bryozoans seem to be poor competitors for space in coral reefs, being often displaced by other sessile animals such as sponge, ascidians and other bryozoans, such as the cheilostome bryozoans.

And this is what we have for today. A beautiful organism whose life history is completely unknown.

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References:

Reeflex. Disporella violacea. Available at < https://www.reeflex.net/tiere/6412_Disporella_violacea.htm >. Access on 25 March 2021.

Wikipedia. Cyclostomatida. Available at < https://en.wikipedia.org/wiki/Cyclostomatida >. Access on 25 March 2021.

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Friday Fellow: Seashore Springtail

by Piter Kehoma Boll

Insects and their six-legged relatives are predominantly land and freshwater species, with very few living in the sea. One of these few species is the springtail Anurida maritima, known as the seashore springtail because this is exactly where it is found.

The preferred habitat of the seashore springtail are rocky or muddy shores with crevices where they can hide when the tide gets high. They are found especially in the Atlantic coast of Europe and North America, but can reach the southern portions of South America and Africa as well.

Several seashore springtails in England. Photo by Calum McLennan.*

During the low tide, they walk around the shore looking for food, which consists mostly of dead animals, especially gastropods. The seashore springtail is, in fact, considered a very important scavenger where it occurs. About one hour before the tide gets high or when the sky darkens because rain is coming, they run toward the crevices that they inhabit and where they build their nests. Since their behavior is governed by the tide and not the day, they have a circatidal rhythm that lasts about 12.4 hours, which helps adjust it as the tide slightly changes from one day to the next as the moon moves around the earth.

Seashore springtails gathering inside the exoskeleton of a dead crab. Photo by Mary Johnson.*

They prefer places that get protected from the water current, especially where there are roots or other vegetative structures that increase protection and surface. Hundreds of springtails can get together in a single nest and get surrounded by a large air bubble when the seawater fills the space. And there they wait until the tide gets low again. They also use those nests to molt and lay their eggs, thousands of them, forming a sort of collective nest.

During winter, they all die and let only their eggs behind. In spring the eggs hatch and the shore gets full of them again, all eager to explore and eat as many dead snails as possible.

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References:

Joosse, E. N. (1966). Some observations on the biology of Anurida maritima (Guérin),(Collembola). Zeitschrift für Morphologie und ökologie der Tiere57(3), 320-328. https://doi.org/10.1007/BF00407599

King, P., Pugh, P. J. A., Fordy, M. R., Love, N., & Wheeler, S. A. (1990). A comparison of some environmental adaptations of the littoral collembolans Anuridella marina (Willem) and Anurida maritima (Guérin). Journal of Natural History24(3), 673-688. https://doi.org/10.1080/00222939000770461

Manica, A., McMeechan, F. K., & Foster, W. A. (2001). An aggregation pheromone in the intertidal collembolan Anurida maritima. Entomologia experimentalis et applicata99(3), 393-395. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.709.8452&rep=rep1&type=pdf

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Friday Fellow: Elegant Clathrulina

by Piter Kehoma Boll

It’s been 84 years since the last time we had a free-living protist as a fellow here. Today’s fellow is a freshwater shape-shifter known as Clathrulina elegans. It obviously lacks a common name, so I decided to call it the elegant clathrulina.

Adult elegant clathrulinas live inside a round organic capsule measuring about 50 µm in diameter. The cell does not occupy the whole capsule, but can move freely inside it. The surface of the capsule has several oval or polygonal openings measuring about 6 µm in diameter. The cell extends very thin pseudopods (filopods) through every opening of the capsule and uses them to capture food, usally smaller protists. These pseudopods arise from cone-like projections at the surface of the cell. Up to three pseudopods can come out of the same projection, but all three pass through different openings of the capsule. Two pseudopods never share the same opening. The capsule has a long stalk, about 150 to 200 µm in length, which attaches the organism to the substrate.

Clathrulina elegans with the capsule, the stalk, the cell and the pseudopods. Credits to Steffen Clauss, extracted from http://www.wunderkanone.de/Heliozoans/photos/

Under favorable conditions, the cells grow inside the capsule and their nucleus suffers mitosis without the whole cell dividing. If the conditions suddenly become unfavorable, the cell divides into several cells and they turn into cysts, which remain inert inside the capsule until the conditions become favorable again.

Empty capsule. Photo by Damon Tighe.*

If the ideal conditions persist, the multinucleated cell eventually divides into several daughter cells. All but one of them leave the capsule and turn into either an amoeboid shape or a biflagellate shape. These amoeboid and biflagellate stages move around until they find a suitable substrate to settle, where they transform again into an adult form. This transformation is complex and starts by a complete change in shape of the cell, which becomes kind of like a sphere, and one large pseudopod is formed to become the stalk. After the stalk is formed, the cytoplasm inside the stalk retracts, letting it hollow, and several vacuoles are formed below the cell membrane, forcing the cell to be separated into an outer part that will develop into the capsule and an inner part that will remain as the cell proper.

The elegant clathrulina can be found in freshwater environments in many parts of the world. However, as it is common among unicellular organism, this may actually be a complex of several species. As usual, there are no studies to clarify the true diversity of this and many other protists.

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References:

Bardele, C. F. (1972). Cell cycle, morphogenesis, and ultrastructure in the pseudoheliozoan Clathrulina elegans. Zeitschrift für Zellforschung und Mikroskopische Anatomie130(2), 219-242. https://doi.org/10.1007/BF00306959

Foulke, S. G. (1884). Some phenomena in the life-history of Clathrulina elegans. Proceedings of the Academy of Natural Sciences of Philadelphia, 17-19. https://www.jstor.org/stable/4060940

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

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Friday Fellow: New Guinea Flatworm

by Piter Kehoma Boll

We learned last week about the giant African snail and how it spread around the world, harming several ecosystems. By the beginning of the 1980s, the giant African snail was a pest on the island of Guam, but suddenly its numbers started to drop and the cause was the accidental introduction of another species on the island, the New Guinea flatworm, Platydemus manokwari.

New Guinea Flatworm in Indonesia. Foto by Franz Anthony.*

Discovered in the forests around the city of Manokwari in New Guinea, more precisely in the province of West Papua, Indonesia, the New Guinea flatworm were at first just another land planarian like many others found around Australasia and the Indo-Malaya ecozones. Measuring about 60 mm in length, 7 mm in width and only 2 mm in thickness, the New Guinea flatworm has a dark-brown, almost black dorsum with a fine yellow median line, while the ventral side has a beige color. Belonging to the tribe Rhynchodemini of land planarians, it has only two eyes near the anterior end and they are considerably large compared to the eyes of land planarians of other tribes and subfamilies and even have a simple lens over their pigment cup, meaning it probably sees better than most planarians.

Anterior end of the New Guinea flatworm. The right eye is visible as a black dot. Credits to Justine et al. (2014).**

As all, or most, land planarians, the New Guinea flatworm is a predator and its favorite prey seems to be snails, which made it become a successful control method against the giant African snail in Guam. Due to this success, the New Guinea flatworm was deliberately introduced in Bugsuk, a small island of the Philippines. About 20 months after its introduction, its population had grown significantly and the population of the giant African snail had sharply decreased.

Specimen in Guam. Photo by Brenden Holland.*

During the following years, the interested in the New Guinea flatworms as biological control increased and the species was introduced either deliberately or accidentally in many Pacific islands. However, around the 1990s, the situation has already turned into a nightmare. One of the most severely affected areas were the Ogasawara Islands in Japan. These islands used to have a very rich snail fauna but 10 years after the introduction of the New Guinea flatworm, most species were extinct. However, despite removing most snails from the islands, the population of the New Guinea flatworm continued to be large and soon it was discovered that it could also feed on earthworms, nemerteans, woodlice and even other land planarians. Its threat, therefore, goes way beyond the snails.

Although widespread across many Pacific islands, the New Guinea flatworm remained restricted to this area of the world for some time, but things changed in 2014 when it was reported in France. Only one year later, in 2015, it was found in the southern United States and the Caribbean. By 2018 it was recorded in Thailand and, to turn things worse, it revealed to be another host of the parasitic nematode Angiostrongylus cantonensis, just like the giant African snail.

Specimen in Florida, USA. Photo by Luca Catanzaro.*

It should come as no surprise that the New Guinea flatworm is also considered one of the top 100 invasive species. Its recent spread across Europe and the Americas means that a new wave of extinctions caused by our recklessness it about to begin.

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References:

Chaisiri, K., Dusitsittipon, S., Panitvong, N., Ketboonlue, T., Nuamtanong, S., Thaenkham, U., Morand, S., & Dekumyoy, P. (2018). Distribution of the newly invasive New Guinea flatworm Platydemus manokwari (Platyhelminthes: Geoplanidae) in Thailand and its potential role as a paratenic host carrying Angiostrongylus malaysiensis larvae. Journal of Helminthology, 1–9. https://doi.org/10.1017/S0022149X18000834

Justine, J.-L., Winsor, L., Gey, D., Gros, P., & Thévenot, J. (2014). The invasive New Guinea flatworm Platydemus manokwari in France, the first record for Europe: Time for action is now. PeerJ, 2, e297. https://doi.org/10.7717/peerj.297

Justine, J.-L., Winsor, L., Barrière, P., Fanai, C., Gey, D., Han, A. W. K., La Quay-Velázquez, G., Lee, B. P. Y.-H., Lefevre, J.-M., Meyer, J.-Y., Philippart, D., Robinson, D. G., Thévenot, J., & Tsatsia, F. (2015). The invasive land planarian Platydemus manokwari (Platyhelminthes, Geoplanidae): Records from six new localities, including the first in the USA. PeerJ, 3, e1037. https://doi.org/10.7717/peerj.1037

Kawakatsu, M., Oki, I., Tamura, S., Itô, H., Nagai, Y., Ogura, K., Shimabukuro, S., Ichinohe, F., Katsumata, H., & Kaneda, M. (1993). An extensive occurrence of a land planarian, Platydemus manokwari de Beauchamp, 1962, in the Ryûkyû Islands, Japan (Turbellaria, Tricladida, Terricola). 陸水生物学報 (Biology of Inland Waters), 8, 5–14.

Muniappan, R., Duhamel, G., Santiago, R. M., & Acay, D. R. (1986). Giant African snail control in Bugsuk island, Philippines, by Platydemus manokwari. Oléagineux, 41(4), 183–186.

Ohbayashi, T., Okochi, I., Sato, H., & Ono, T. (2005). Food habit of Platydemus manokwari De Beauchamp, 1962 (Tricladida: Terrricola: Rhynchodemidae), known as a predatory flatworm of land snails in the Ogasawara (Bonin) Islands, Japan. Applied Entomology and Zoology, 40(4), 609–614. https://doi.org/10.1303/aez.2005.609

Sugiura, S. (2010). Prey preference and gregarious attacks by the invasive flatworm Platydemus manokwari. Biological Invasions, 12(6), 1499–1507. https://doi.org/10.1007/s10530-009-9562-9

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

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

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Filed under Conservation, flatworms, Friday Fellow