Friday Fellow: Pacific Waminoa

by Piter Kehoma Boll

A long time ago I talked about a polemic group of bilaterian animals, the acoelomorphs, whose exact phylogenetic position is uncertain but the evidence is starting to build up toward the idea that they are part of the first branch of bilaterians to diverge from the others, so that they are neither protostome nor deuterostomes. No acoelomorph has been presented as a Friday Fellow before, so today it is time for their debut. The species I selected is a very interesting one. Its name is Waminoa litus and, of course, it lacks a common name, so I decided to call it the Pacific waminoa because it is found in the Pacific, especially around Australia.

A marine species, the Pacific waminoa has the typical anatomy of the acoels, the subgroup of acoelomorphs to which it belongs. It lacks, for example, a gut, and its mouth opens directly into the internal tissues. The mouth is located at the venter, like in many flatworms, such as planarians. In fact, acoelomorphs were for a long time thought to be flatworms until molecular analyses revealed that they are not.

If you ever find small golden flakes on the surface of corals in Eastern Australia and nearby regions, you are most likely seeing several Pacific waminoa. Photo by Anne Hoggett.*

With a flat and circular, slightly heart-shaped body, the Pacific waminoa lives on the surface of corals. They are, in fact, kind of an ectoparasite to corals, as they feed on the coral’s mucus. But more than that, the Pacific waminoa also harbors symbiotic dinoflagellates (zooxanthellae) living directly inside its parenchyma, the tissue that fills their body. Zooxanthellae are famous as common symbiotic organisms living inside corals, and they share part of the nutrients they make via photosynthesis with their host. The corals in which the Pacific waminoa lives also harbor zooxanthellae. However, while all zooxanthellae living in the corals belong to the genus Symbiodinium, the ones living in the Pacific waminoa belong to two genera, Symbiodinium and Amphidinium. This is very unusual, as zooxanthellae belonging to two different genera in the same animal is a very rare occurrence. The beautiful golden color of the Pacific waminoa is a direct result of the presence of the zooxanthellae.

Several waminoas, likely Waminoa litus, on a coral in the Philippines. Photo by Franca Wermuth.*

At first it was thought that, due to this close relationship between these acoels and the corals, the lineages of Symbiodinium living inside both organisms would be closely related, but this is not the case. Molecular studies revealed that Symbiodinium living in the Pacific waminoa are not the same that live inside the corals, which indicates that both organisms acquired them independently, i.e., the Pacific waminoa does not captures them from the coral. In fact, they are passed directly from the mother to the offspring inside the eggs. The Pacific waminoa is born with the dinoflagellates already inside it.

The Pacific waminoa is, therefore, an incredible creature not only because it belongs to a very divergent lineage of bilaterian animals but because it is the only case known in bilaterians about symbionts being transferred directly from the mother to the offspring. Perhaps one day the zooxanthellae will evolve into a new organelle of a clade that will evolve from this amazing species.

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References:

Barneah, O., Brickner, I., Hooge, M., Weis, V. M., LaJeunesse, T. C., & Benayahu, Y. (2007). Three party symbiosis: acoelomorph worms, corals and unicellular algal symbionts in Eilat (Red Sea). Marine Biology, 151(4), 1215-1223.

Hikosaka-Katayama, T., Koike, K., Yamashita, H., Hikosaka, A., & Koike, K. (2012). Mechanisms of maternal inheritance of dinoflagellate symbionts in the acoelomorph worm Waminoa litus. Zoological science, 29(9), 559-567.

Kunihiro, S., & Reimer, J. D. (2018). Phylogenetic analyses of Symbiodinium isolated from Waminoa and their anthozoan hosts in the Ryukyu Archipelago, southern Japan. Symbiosis, 76(3), 253-264.

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

Friday Fellow: Japanese Pauropod

by Piter Kehoma Boll

We reached one more moment in which things get a little disheartening because it is time to talk about another group of neglected organisms, the pauropods. These very small arthropods measure only a few milimeters in length and belong to the subphylum Myriapoda, being related to the most popular centipedes and milipedes.

I was unable to have easy access to good information of any species, so I decided to talk about the only one of which I found a good photograph and that was determined to the species level, Eurypauropus japonicus, which I decided to call the Japanese pauropod.

The Japanese pauropod measures less than 2 mm in length, usually between 1.5 and 1.7 mm. The adults have a pair of antennae and nine pairs of legs, one in each segment behind the head, except for the last (one, or two?) segment. The dorsal side is covered by five heavily sclerotized plates, which gives the impression that they have fewer segments.

The only photo of a pauropod determined to the species level, Eurypauropus japonicus, that I could find. Thanks to Ryosuke Kuwahara.*

Like all pauropods, the Japanese pauropod avoids light, living in dark humid places in the forest soil, often inside and below rotten wood. Pauropods in general are not found in large densities, and I think the same applies to the Japanese pauropod. Its diet is unknow, but it most likely feeds on fungi and, perhaps, live or decaying plant matter as well.

Details about its reproduction are unknown as well. Based on information of other pauropods, mating probably occurs with the males depositing a spermatophore (a sperm-filled sac) on the substrate, which is then collected by the female to fertilize her eggs. Newly hatched pauropods have only three pairs of legs, but this number increased at every mold until reaching, in the Japanese pauropod, the maximum of nine pairs.

The pauropods are one more group of organisms that, because of their lack of cuteness and “beauty”, do not attract the attention of the general public, and this is also reflected in the lack of interest in studying them by biologists in general. How can we change that?

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References:

HAGINO, Y., & SCHELLER, U. (1985). A new species of the genus Eurypauropus (Pauropoda: Eurypauropodidae) from central Japan. Proceedings of the Japanese Society of Systematic Zoology (Vol. 31, pp. 38-43). The Japanese Society of Systematic Zoology.

Wikipedia. Pauropoda. Available at < https://en.wikipedia.org/wiki/Pauropoda >. Access on 14 October 2021.

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

Friday Fellow: Flaming Katy

by Piter Kehoma Boll

Today’s species is a very popular ornamental plant and I am sure you have already seen it somewhere, or perhaps everywhere. A succulent of the family Crassulaceae, its scientific name is Kalanchoe blossfeldiana. But do you know how to pronounce Kalanchoe? I have heard all sorts of pronunciations, but the best way to understand how to say this word is knowing its origin. It comes from a Chinese word, which was registered as ‘Kalanchauhuy’. The word is probably 伽藍菜 (gāláncài) and, if this is really the case, the most adequate pronunciation in English would be KAL-ən-choy /ˈkælənt͡ʃɔɪ̯/. Anyway, here we will call it flaming Katy, one of its common names. Let’s talk about the plant itself now.

Flaming Katies are often cultivated in small flower pots with a single plant per pot. Photo by Veronica Russell**.

The flaming Katy is native from Madagascar, growing in nutrient-rich soils of mountain plateaus. It is a relatively slow-growing plant with smooth succulent leaves and reaches a maximum height of about 45 cm in two to five years. It flowers in late autumn and early winter, producing compound inflorescences with small four-petal flowers, although some cultivars have double flowers, with an increased number of petals.

As most succulents, the flaming Katy is very easy to cultivate. It does not require much water, although it needs to get direct sunlight or at least intense indirect sunlight. As a result, it has become a very popular ornamental plant and many different cultivars have been developed, including flowers of many different colors, such as white, yellow, orange, red, pink and magenta. Phytochemistry studies have revealed considerable differences in the amount of different types of flavonoids in the flowers of different colors. These differences could help direct the crossing of existing varieties to create new colors, especially blue.

Several cultivars with different colors, as well as simple and double flowers. Photo by Einav Porat.*

Due to its ease of cultivation, the flaming Katy is also frequently used in studies on several fields, including genetics, plant physiology, phytochemistry and ecology. Nevertheless, it does not seem to be considered a model organism, at least not yet, probably because most studies are focused on improving the plant for ornamental use by producing new varieties with different colors and shapes or with increased resistance to certain environmental conditions. But perhaps one day we will find out that this lovely and popular plant can be useful beyond its ornamental role in our gardens.

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References:

Asrar, A. A., Abdel-Fattah, G. M., Elhindi, K. M., & Abdel-Salam, E. M. (2014). The impact of arbuscular mychorrhizal fungi in improving growth, flower yield and tolerance of kalanchoe (Kalanchoe blossfeldiana Poelin) plants grown in NaCl-stress conditions. Journal of Food, Agriculture & Environment, 12(1), 105-112.

Nielsen, A. H., Olsen, C. E., & Møller, B. L. (2005). Flavonoids in flowers of 16 Kalanchoe blossfeldiana varieties. Phytochemistry, 66(24), 2829-2835. https://doi.org/10.1016/j.phytochem.2005.09.041

Wikipedia. Kalanchoe blossfeldiana. Available at < https://en.wikipedia.org/wiki/Kalanchoe_blossfeldiana >. Access on September 20, 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-NonCommercial 4.0 International License.

Friday Fellow: Fragile Sandpipe

by Piter Kehoma Boll

The deep sea is full of bizarre but wonderful creatures. Not only animals get weird in the depths of the ocean, but other organisms as well. One of these is Syringammina fragilissima, or the fragile sandpipe, as I decided to call it. Found in the northern Atlantic Ocean, the fragile sandpipe may be hard to notice at first on the dirty floor of the ocean, but if you pay enough attention you may notice some structures that look like simple sand mounds.

Two fragile sandpipes on the ocean floor indicated by arrows. Extracted from Morris et al. (2014).

Measuring more than 10 cm in diameter, the fragile sandpipe is actually a unicellular organism, more precisely a foraminifer of a group known as Xenophyophorea. Their cell consists of a series of interconnected organic tubes inside of which the cytoplasm is located. The cytoplasm holds several nuclei but is a single, continuous cell across the whole structure. An adhesive secretion on the surface of the tubes makes sand and shells of smaller organisms to glue on it, creating a case inside of which the organism remains. The remains of the fragile sandpipe’s digestion (its feces, one could say) accumulate as pellets (stercomata) in some areas of the pipes, eventually forming large strings and masses of this material.

A somewhat cleaner xenophyophore, probably a specimen of Syringammina fragilissima.

The whole structure of the organism is very fragile and tends to break appart very easily when handeld, hence the name fragilissima.

As the fragile sandpipe grows, the cytoplasm retracts from some of the older parts of the tubes, letting them hollow. Other deep sea organisms, including worms (nematodes and annelids), crustaceans and especially smaller foraminifers, end up using these hollow areas as their home. Some species living inside them are pretty rare elsewhere, making the fragile sandpipe a very important species for the deep sea communities where it is found.

The whole skeleton on a fragile sandpipe (top) and smaller foraminifers living inside the empty tubes (bottom). Extracted from Hughes et al. (2004).

Due to its fragility and the inaccessible region where it is found, very little is known about the ecology of the fragile sandpipe. Some analysis suggest that it may be a deposit feeder, ingesting organic matter and live organisms from the sediments around it. An analysis of lipid content also suggested that the fragile sandpipe may feed on bacteria that grow in its fecal pellets. If this is true, one could say that it cultivates its own food in its own feces. Very practical!

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More Foraminifers:

Friday Fellow: Tepid Ammonia (on 6 May 2016)

Friday Fellow: Bubble Globigerina (on 30 June 2017)

Friday Fellow: Pink Miniacina (on 12 January 2018)

More Giant Unicellular Organisms:

Friday Fellow: Sailor’s Eyeball (on 8 April 2016)

Friday Fellow: Giant Gromia (on 21 August 2018)

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References:

Hughes, J. A., & Gooday, A. J. (2004). Associations between living benthic foraminifera and dead tests of Syringammina fragilissima (Xenophyophorea) in the Darwin Mounds region (NE Atlantic). Deep Sea Research Part I: Oceanographic Research Papers, 51(11), 1741-1758.

Laureillard, J., Méjanelle, L., & Sibuet, M. (2004). Use of lipids to study the trophic ecology of deep-sea xenophyophores. Marine Ecology Progress Series, 270, 129-140.

Morris, E.S., Stamp, T. & Goudge, H. (2014) Analysis of video and still images to characterise habitats and macrobenthos of the Wyville Thomson Ridge SCI and Faroe-Shetland Sponge Belt Scottish Nature Conservation MPA Proposal (1512S). JNCC Report No: 532.

Friday Fellow: Sickle Paucumara

by Piter Kehoma Boll

As a planariologist, I obviously love planarians and find them amazing creatures. Among the more than 300 Friday Fellows we had until now, only three were planarians, and all were land planarians. So I think it is more than time to bring you an aquatic species, but instead of going to the most famous freshwater species, let’s present a marine one.

Marine planarians form a very diverse but poorly studied group. Today’s species is named Paucumara falcata, which I decided to name the sickle paucumara. This species was described only two years ago, in 2019, and is one of the two species of the genus Paucumara.

All currently known specimens of the sickle paucumara were found in the coastal waters of Shenzhen, in China. They measure about 4 mm in length and 0.5 mm in width. They are, therefore, very small even from a planarian perspective. The body is mostly transparent, with the intestine easily seen through the skin, especially when filled with food. Two very small kidney-shaped eyes lie near the anterior, somewhat triangular end. There are three yellowish-white bands running transversally through the body, one at the anterior tip, one right behind the eyes and one near the posterior end. The region between the two first yellowish-white bands is brownish, and a longitudinal yellowish-white band runs from the second transversal one posteriorly until about one third of the body length, forming a T shape. There are also some yellowish white speckles scattered throughout the dorsum.

Two adult specimens of the sickle paucumara. Extracted from Chen et al. (2019).

Little is known about the ecology of this species, mostly because it has been just recently discovered. However, it has been reared in the laboratory, where groups of individuals can feed together on larger invertebrates, including larger planarians.

The most interesting thing observed in this species is its mating behavior. In the laboratory, a specimen that was willing to mate approached a potential partner and started to “dance” beside it, swinging its tail from side to side and touching the body of the potential partner with it. If the approached worm accepted the invitation, it raised its tail from the substrate and to expose its gonopore (the genital opening) and the first worm did the same. They then touched their gonopores and started mating.

See the sickle used to anchor one worm on the other while they mate. Extracted from Chen et al. (2019).

The male copulatory apparatus of the sickle paucumara has a sickle-shaped musculo-parenchymatic organ with a chitinized stylet at the tip, hence the name falcata (sickled). When a pair is mating, each worm perforates the body of the other with this sickle, thus ensuring that they will remain anchored to each other during the about 10 minutes that the mating process lasts. After the worms have exchanged sperm, they detach their copulatory apparatuses but remain together and twist their bodies around each other, forming a spiral. Why? No one knows… at least yet.

Watch they mate and twist into a spiral!

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References:

Chen, J.-J., Li, W.-X., Sluys, R., Wu, M.-Q., Wang, L., Li, S.-F., & Wang, A.-T. (2019). Two new species of marine flatworm from southern China facilitate determination of the phylogenetic position of the genus Nerpa Marcus, 1948 and the histochemical structure of the nervous system in the genus Paucumara Sluys, 1989 (Platyhelminthes, Tricladida, Maricola). Zootaxa, 4568(1), 149–167. https://doi.org/10.11646/zootaxa.4568.1.9

Yang, Y., Li, J.-Y., Sluys, R., Li, W.-X., Li, S.-F., & Wang, A.-T. (2020). Unique mating behavior, and reproductive biology of a simultaneous hermaphroditic marine flatworm (Platyhelminthes, Tricladida, Maricola). Invertebrate Biology, 139(1), e12282. https://doi.org/10.1111/ivb.12282

Friday Fellow: Common Liverwort

by Piter Kehoma Boll

Four liverworts were previously presented here, but it is more than time to talk about the liverwort, the species that made this group of plants receive its common name. Marchantia polymorpha is its scientific name, and in English it is often referred to as the common liverwort.

Widespread throughout the Holarctic ecozone (i.e., North America, Europe, Northern Asia), the common liverwort has, like all liverworts, its gametophyte phase as the dominant one. It has flattened thallus up to 10 cm long and 2 cm wide, often green but sometimes becoming brownish or purple. The overall shape of the thallus resembles that of liver, hence the name liverwort.

Common liverwort growing among some mosses. The small circular structures on the thalli are gemmae cups. Photo by Krzysztof Ziarnek.*

The gametophyte of the common liverwort is either male or female. Both plants produce umbrella-like structures, the gametophores, in which gametes are produced. The female gametophore has a star-like structure at the top, while the male gametophore has a flatenned disc, sometimes with lobed margins. When the male gametes are mature, they are carried with the water from the rain to the female gametophores, where they will fertilize the female gametes. The zygote will develop into a sporophyte, which grows from the underside of the female gametophore, making it look “fluffy”. The sporophyte, in turn, will produce spores that are released in the environment and will germinate to originate new gametophytes.

Male gametophores with a lobed disc shape.

The gametophytes can also reproduce asexually by producing gemmae inside gemmae cups. The gemmaes are small lentil-shaped plants that are released in the environment when drops of water fall into the cups.

Female gametophores with their star shape.

The common liverwort is considered a pioneer plant and colonize exposed soils very frequently. After large wildfires, it can quickly cover the soil of the affected region, thus preventing soil erosion. On the other hand, this quick spread makes it a common weed in gardens and greenhouses. It is also very resistant to high concentrations of lead in the soil, so regions in which this species is very abundant but otherwise few plant species grow can indicate a contaminated soil.

A female gametophore with the fluffy sporophytes growing from it.

Due to its liver-like appearance, the common liverwort was historically used to treat liver ailments through the doctrine of signatures, which stated that a plant resembling the shape of a human organ could be used to treat diseases of that organ.

Closeup of a gemma, a small structure for asexual reproduction. Credits to Wikimedia user Des_Callaghan.*

In recent decades, the interest on the common liverwort as a model organism started to grow. It has a quick life cycle, is easily cultivated and has a relatively small genome, which makes it interesting to study several biological aspects, especially the evolution of plants. Its genome has been sequenced only very recently though, in 2017, but has already shown to help us understand the evolution of plants to conquer the land.

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Previous liverwort fellows:

Floating Crystalwort (on 18 November 2016)

Flat-leaved Scalewort (on 20 October 2017)

Crescent-cup liverwort (on 15 June 2018)

Common Pellia (on 28 August 2020)

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References:

Bowman, J. L., Kohchi, T., Yamato, K. T., Jenkins, J., Shu, S., Ishizaki, K., … & Schmutz, J. (2017). Insights into land plant evolution garnered from the Marchantia polymorpha genome. Cell, 171(2), 287-304. https://doi.org/10.1016/j.cell.2017.09.030

Shimamura, M. (2016). Marchantia polymorpha: taxonomy, phylogeny and morphology of a model system. Plant and Cell Physiology, 57(2), 230-256. https://doi.org/10.1093/pcp/pcv192

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

Friday Fellow: Striped Barnacle

by Piter Kehoma Boll

Barnacles are a peculiar group of sessile crustaceans and are common worldwide in the oceans, sometimes even living on the surface of marine animals such as mollusks, whales and turtles. Until now only one barnacle was featured here, a goose barnacle. So today we will know a species of the most common acorn barnacles, Amphibalanus amphitrite, known as the striped barnacle, purple acorn barnacle or Amphitrite’s rock barnacle.

The purple vertical stripes give the striped barnacle its name. Photo by iNaturalist user julieskrinni.*

The striped barnacle has the typical conical shape of acorn barnacles formed by six calcareous plates surrounding the body. The opening at the top has a diamond shape and is protected by a movable lid formed by two plates. The plates of the shell have a series of vertical brown to purple stripes, hence the name striped barnacle. To eat, the striped barnacle opens the lid and extends its long feathery legs, called cirri, through the opening to capture food particles from the water.

Submerged striped barnacles with their cirri exposed. Photo by Jason Lee Boswell.*

The exact origin of the striped barnacle is unknown, but it is likely native from the Indian ocean. However, due to human activities, it has been carried across the whole world and is now found in warm and temperate waters of all oceans.

As typical of barnacles, the striped barnacle is hermaphrodite. To reproduce, they use a very long penis that they insert inside adjacent barnacles to release sperm. The fertilized eggs are released in the water and develop first into a nauplius larva os crustaceans and later into the cyprid larva, which is the last stage before they become adults. The cyprid looks for an adequate substrate to settle and, once finding it, starts to secrete a glycoproteinous substance to attach the head on the substrate and undergoes the final metamorphosis to became a juvenile barnacle. They continue to molt as they keep growing after attaching to the substrate, but the calcarous plates do not molt with them, but continue to grow like the shell of a mollusk.

Several striped barnacles growing on the back of a horseshoe crab. Photo by iNaturalist user ozarkpoppy.*

The striped barnacle can grow on human-made structures, such as ships, pipes and other constructions exposed to the tides, and can become a nuisance, as its presence can decrease the efficacy of some of the colonized structures. As a result, it has become a target species of studies and is even a model organism for the study of larval settlement of barnacles. Even its genome has already been sequenced and several technologies are being tested to reduce its ability to colonize ships.

Not all studies with this species are directed to ways to getting rid of it, though. Due to the ease of breeding it in the lab, the striped barnacle is also used to study, for example, the impact of microplastics and ocean acidification on marine life.

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References and further reading:

Bhargava, S., Chen Lee, S. S., Min Ying, L. S., Neo, M. L., Lay-Ming Teo, S., & Valiyaveettil, S. (2018). Fate of nanoplastics in marine larvae: a case study using barnacles, Amphibalanus amphitrite. ACS Sustainable chemistry & engineering, 6(5), 6932-6940. https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.8b00766

Burden, D. K., Spillmann, C. M., Everett, R. K., Barlow, D. E., Orihuela, B., Deschamps, J. R., … & Wahl, K. J. (2014). Growth and development of the barnacle Amphibalanus amphitrite: time and spatially resolved structure and chemistry of the base plate. Biofouling, 30(7), 799-812. https://doi.org/10.1080/08927014.2014.930736

Maréchal, J. P., & Hellio, C. (2011). Antifouling activity against barnacle cypris larvae: Do target species matter (Amphibalanus amphitrite versus Semibalanus balanoides)?. International Biodeterioration & Biodegradation, 65(1), 92-101. https://doi.org/10.1016/j.ibiod.2010.10.002

McDonald, M. R., McClintock, J. B., Amsler, C. D., Rittschof, D., Angus, R. A., Orihuela, B., & Lutostanski, K. (2009). Effects of ocean acidification over the life history of the barnacle Amphibalanus amphitrite. Marine Ecology Progress Series, 385, 179-187. https://doi.org/10.3354/meps08099

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Friday Fellow: Eelgrass Labyrinthula

by Piter Kehoma Boll

In the 1930s, a devastating disease spread across the Atlantic populations of the common eelgrass, killing 90% of the plants. The disease started by destructing the plant’s chloroplasts, turning the leaves white, followed by a rot of the tissues that spread until the whole plant was dead.

Although the agent causing the disease was already suggested back then, it was only confirmed during a second, smaller recurrence in the 1980s. The responsible is a marine fungi-like parasite known as Labyrinthula zosterae, which I decided to call the eelgrass labyrinthula.

Dark marks of rotten tissue in the common eelgrass caused by the eelgrass labyrinthula. Extracted from Short (2014).

The eelgrass labyrinthula belongs to a peculiar group of organisms that were at first classified as a weird group of slime molds but are now known to be heterokonts, thus more closely related to diatoms, brown algae and oomycetes, for example. They are colonial organisms and their colony is quite interesting in its arrangement. The individual vegetative cells are spindle-shaped (fusiform) and measure from 15 to 20 µm in length by 3 to 5 µm in width. They are often translucent, sometimes pale yellow, and are filled with lipid droplets.

Vegetative cells of the eelgrass labyrinthula. The ectoplasmic net can be seen as thin white extensions. Extracted from theredshrimp.com

The cells produce together a net formed by ectoplasm (cytoplasm) that is excreted from the cells and is surrounded by a cell membrane, thus becoming kind of like a large maze-like cell inside of which the individual cells live. This net lacks a cell wall and organelles, though. The cells can slide across this net, using it as a “road”.

There are two modes or reproduction known until now. The first is simply by cell division through mitosis. Another form of reproduction is by zoosporulation, which starts with several vegetative cells aggregating and fusing into a single plasmodium-like structure. Later, this plasmodium divides back into round, enlarged presporangia, which then divide internally into eight zoospores, which are then released in the environment. The zoospores are cells with two flagella and a stigma (eyespot), very similar to the typical cell of other heterokonts, and will differentiate back into vegetative cells.

The infection of the common eelgrass by the eelgrass labyrinthula occurs by direct contact of a healthy plant with an infected one or with dettached, infected parts. The parasite acts by dissolving the plant’s cell wall and spreading across the tissues, destroying the cells and likely feeding on them. Recent studies, however, discovered that the eelgrass labyrinthula is quite common in eelgrass populations but most strains are not very virulent. In fact, it is likely that the eelgrass labyrinthula is part of the “normal” protist biota associated with the common eelgrass and it only becomes a threat when the plant experience some sort of stress induced by other conditions.

Anyway, there is still much to be discovered about this protist and its dubious intentions.

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References:

Brakel, J., Werner, F. J., Tams, V., Reusch, T. B., & Bockelmann, A. C. (2014). Current European Labyrinthula zosterae are not virulent and modulate seagrass (Zostera marina) defense gene expression. PLoS One, 9(4), e92448. https://doi.org/10.1371/journal.pone.0092448

Muehlstein, L. K., Porter, D., & Short, F. T. (1991). Labyrinthula zosterae sp. nov., the causative agent of wasting disease of eelgrass, Zostera marina. Mycologia, 83(2), 180-191. https://doi.org/10.1080/00275514.1991.12025994

Ralph, P. J., & Short, F. T. (2002). Impact of the wasting disease pathogen, Labyrinthula zosterae, on the photobiology of eelgrass Zostera marina. Marine Ecology Progress Series, 226, 265-271.

Short, Fred, “Eelgrass Wasting Disease: an Overview” (2014). Salish Sea Ecosystem Conference. 34.
https://cedar.wwu.edu/ssec/2014ssec/Day1/34

Friday Fellow: Common Eelgrass

by Piter Kehoma Boll

Today we reach 300 Friday fellows, dear readers! And, as usual we will celebrate this presenting two species today.

Due to this special occasion, let’s present a special species as well, the common eelgrass, Zostera marina. But if it is special, why is it called common?

Well, this species is special because it is a marine flowering plant. Although flowering plants have conquered the planet across almost all its biomes, they are pretty rare in the sea, but the common eelgrass is one exception. And it is such a successful species that it can be found around the whole northern hemisphere in the Atlantic and Pacific oceans, including the Mediterranean and the Black Sea.

Common eelgrass at the northwest coast of the USA. Photo by John Brew.*

The ideal habitat for the common eelgrass are cold, clear and shallow waters, although not too shallow, as it likes to remain completely submerged. Its stem is a rhizome that grows inside the sandy or muddy substrate and from which long slender leaves emerge. The leaves have about 1 cm in width but their length can vary from a few centimeters to more than one meter depending on the water depth and turbidity.

The common eelgrass is able to reproduce entirely underwater. The flowers arise from the base of the leaves and form an elongate inflorescence with alternating female and male flowers that is enclosed in a sheath. Female flowers develop first, exposing their styles and waiting to be pollinated by the pollen of other plants. The pollen is specially adapted to be transported through the water. After the female flowers have been pollinated, their styles retract and the male flowers expose their anthers to release pollen in the water. The fruits start to develop and form a small transparent sack that contains the seed. After seed maturation, the fruits are released in the water to find a substrate to germinate.

Flowering stages of the common eelgrass. (1) female flowers expose their styles; (2) pollinated female flowers retract to start seed development; (3) male flowers expose the anthers and release pollen; (4) seeds starting to mature; (5) mature seeds ready to be released. Extracted from Infantes & Moksnes (2018).

Human populations have used the common eelgrass for centuries or even millenia. They can be harvested to be used as a fertilizer or fodder to cattle, the dried leaves can be used to stuff mattresses and they can also serve as food, with both the leaves and seeds being edible.

The stable environment formed by the common eelgrass is an important habitat for many marine species, including animals, algae and even bacteria, which use them as shelter, reproductive site or even feed on the plants. However, the increasing turbidity in coastal waters caused by human activities, especially water pollution, threatens many populations of this species, as it cannot adequately photosynthesize if light is blocked in the water column.

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References:

Infantes, E., & Moksnes, P. O. (2018). Eelgrass seed harvesting: Flowering shoots development and restoration on the Swedish west coast. Aquatic botany, 144, 9-19.

Wikipedia. Zostera marina. Available at < https://en.wikipedia.org/wiki/Zostera_marina >. Access on 19 August 2021.

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

Friday Fellow: Fly-Killing Fungus

by Piter Kehoma Boll

You most likely know about the existence of the parasitic fungi of the family Cordycipitaceae that turn insects and other arthropods into “zombies”. I even presented one here already about 5 years ago, the Chinese caterpillar fungus. But zombie-making fungi did not evolve only once and today we will meet another one that also zombifies insects, more precisely flies.

Its scientific name is Entomophthora muscae and I decided to give it the common name fly-killing fungus. While the most famous zombifying fungi belong to the phylum Ascomycota, the fly-killing fungus belongs to the phylum Entomophtoromycota, which until recently was part of the phylum Zygomycota.

Dead fly of the species Scathophaga stercoraria consumed by the fly-killing fungus. Photo by Hans Hillewaert.*

The fly-killing fungus is actually a complex of species that infects a variety of flies, including house flies. Their life start as an asexual spore, the conidium. When the conidium contacts the surface of a fly, it germinates, forming a germ tube that penetrates the cuticle of the fly. When the germ tube reaches the haemocoel, the cavity in which the fly’s haemolymph (blood) is found, it releases some cells (protoplasts) into the haemolymph. The protoplasts are carried to the brain and grow in areas that control the fly’s behavior. From there, the fungus start to produce hyphae that grow through the whole body, slowly digesting the internal organs. When the fly is about to die, it crawls to a high point in the vegetation or other available structure, stretches the hind legs and opens the wings and eventually dies. Some hours later, the fungus start to produce conidiophores that grow on the surface of the fly. When they are mature, they release conidia into the environment, restarting the cycle.

Dead hoverfly of the species Melanostoma scalare with the conidiophores of the fly-killing fungus coming out of its abdomen. Photo by Wikimedia user TristramBrelstaff.**

The species complex known as Entomophthora muscae can infect a huge variety of flies, including domestic flies, fruit flies, blow flies, mosquitos and many others. As many of the hosts of the fly-killing fungus as medically or economically important species for humans, there have been attempts to “weaponize” this fungus, turning it into a biological control against several fly pests.

This is not an easy task, though. First, the fungus is very sensible to high temperatures and flies can “cure” themselves from the infection by moving to hot environments that inhibit the growth of the fungus. Another problem is that, in order to raise the fungus in the lab, the fungus needs a constant supply of live adults flies.

As in many cases of using biological agents to control pests, there is always the possibility of things going wrong and end up affecting species that were not the original target. The genetic diversity of the fly-killing fungus is not very well known yet, so that we don’t know exactly which fly species each strain (or species) can actually infect.

I hope we don’t end up turning this ecologically innocent fungus into one more villain on the planet due to our misbehavior.

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References and further reading:

Brobyn, P. J., & Wilding, N. (1983). Invasive and developmental processes of Entomophthora muscae infecting houseflies (Musca domestica). Transactions of the British Mycological Society, 80(1), 1-8. https://doi.org/10.1016/S0007-1536(83)80157-0

Kramer, J. P., & Steinkraus, D. C. (1981). Culture of Entomophthora muscae in vivo and its infectivity for six species of muscoid flies. Mycopathologia, 76(3), 139-143. https://doi.org/10.1007/BF00437194

Krasnoff, S. B., Watson, D. W., Gibson, D. M., & Kwan, E. C. (1995). Behavioral effects of the entomopathogenic fungus, Entomophthora muscae on its host Musca domestica: Postural changes in dying hosts and gated pattern of mortality. Journal of Insect Physiology, 41(10), 895-903. https://doi.org/10.1016/0022-1910(95)00026-Q

Wikipedia. Enthomophthora muscae. Available at < https://en.wikipedia.org/wiki/Entomophthora_muscae >. Access on 12 August 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-ShareAlike 3.0 Unported License.