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: Giant Gromia

by Piter Kehoma Boll

Some time ago I introduced a cool unicellular alga, the Sailor’s Eyeball, which can reach about 5 cm in diameter, being one of the largest unicellular organisms known to exist.

Today  we’ll know one more creature of this type, only it is not an alga, but a testate amoeba more closely related to foraminifers. Named Gromia sphaerica, I will here call it the giant gromia.

Specimens of the giant gromia from the Bahamas. Image extracted from Matz et al. (2008).

The giant gromia was first found in the Arabian Sea at depths of more than 1100 m and was formally described in 2000. It lives lying on the substrate and is usually covered by a thin layer of sediment, appearing as small spheres scattered across the sea floor. The body is spherical or grape-shaped but hollow, with the interior filled with fecal material (called stercomata) or other fluids. This spherical cell is covered by a shell, or test, of organic material which shows several small perforations by which thin expansions of the cytoplasm, forming a kind of pseudopod, can be extended. The size of the test can reach up to 3 cm in diameter, being much larger than that of its best known relative, Gromia oviformis.

Several specimens of Gromia sphaerica on the sea floor of the Bahamas with the tracks left by their movement. Extracted from Matz et al. (2008).

In 2008, another population of species was found in the waters around the Bahamas. Specimens there are not as spherical as in the population in the Arabican Sea and  were seen associated with tracks that indicate that these organisms slowly move across the sediment. The tracks clearly resemble some fossil tracks from the Pre-Cambrian period, which are usually considered an indication of the early evolution of multicellular animals. However, this discovery of unicellular organisms being able to produce tracks similar to those associated with animals raises doubt about the time of origin of multicellular animals.

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References:

Gooday AJ, Bowser SS, Bett BJ, Smith CR (2000) A large testate protist, Gromia sphaerica sp. nov. (Order Filosea), from the bathyal Arabian Sea. Deep-Sea Research II 47: 55–73.

Matz MV, Frank TM, Marshall NJ, Widder EA, Johnsen S (2008) Giant deep-sea protists produces bilaterian-like traces. Current Biology 18(23): 1849–1854. https://doi.org/10.1016/j.cub.2008.10.028