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.