Gromia sphaerica
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Gromia sphaerica |
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| Gooday et al., 2000 |
Gromia sphaerica is a kind of wired amoeba-like unicellular organism . They inhabit the seabeds of the deep sea and are unusually large for single-cell organisms.
features
Gromia sphaerica are spherical to grape-shaped, unicameral and have a diameter of 4.7 to 38 millimeters, with an average of 15 millimeters.
The translucent, occasionally slightly brownish, flexible outer shell is multilayered: on top is an extremely thin, granular layer that covers a somewhat thicker, fibrous carrier structure made of proteins . In contrast to related species, which have only one or a few openings, this shell is filled with numerous fine pores evenly distributed over the outer shell. The outlet openings of the pores each lie in the center of a circular projection, seen from above, around which an annular, slightly deepened halo lies. The filopodic pseudopods formed from the protoplasm emerge from the pore opening . Under the fibrous shell lie the so-called “honeycomb membranes” , a typical layer of many fragmentary layers of hexagonal cylinders connected by partitions.
There is a thin, dark green protoplasmic layer below the outer shell . The cavity surrounded by the cell body is empty or there are accumulations of small fecal pills (Stercomata). The feces pills are gray or brown, 10 to 20 micrometers in diameter, sometimes up to 40 micrometers , and fill the entire cavity.
There are indications that Gromia sphaerica have only one nucleus, but this is not certain.
distribution
So far, populations of the species have been discovered in the Arabian Sea and off the Bahamas . They could be detected off the coast of Oman at depths of 1200 to 1600 meters, off the Pakistani coast at depths of up to 1800 meters and off the Bahamas at depths of 750 to 780 meters.
Gromia sphaerica occur on the sea floors of the respective continental slopes in loose, but not liquid sediments that are rich in nutrients such as phosphates , silicates and nitrogen . They are either completely covered (Bahamas) or partially exposed (Oman) embedded in these sediments. The surrounding water contains relatively little oxygen (0.47 ml liter −1 ).
Way of life
Gromia sphaerica move slowly through the sediments, leaving behind a trail that is up to 50 centimeters long, deep and clearly recognizable. However, they do not move actively, but presumably "eat" themselves forward, as it were: they absorb the extremely nutrient-rich top layer of the sediment surrounding them through their pseudoplasm, digest it in the protoplasm and convey it behind them, which creates a free space to the front. into which they roll until they can take up sediment again. The digested sediments are excreted towards the rear, so that a narrow, raised track is formed in the middle of the groove.
The resulting traces show a great resemblance to fossil traces of the Ediacara fauna , which until now were mostly assigned to multicellular organisms. Due to the similarities of the traces in terms of size and structure as well as the existence of similar traces in the Paleoproterozoic , in which there was no multicellular life (e.g. in the Stirling Range Formation ), it is considered possible that these traces are at least partially similar originate from large unicellular organisms.
Occasionally they form groups of two or three individuals.
Systematics
The species was discovered in collections of the RRS Discovery on its Cruise 211 between October and November 1994 off the coast of Oman and was first described in 2000 by a team led by Andrew J. Gooday . Molecular genetic investigations of the species of the genus, which are morphologically difficult to distinguish from one another, confirmed Gromia sphaerica as an independent species and showed some species that were previously not formally described as closest relatives.
Individual evidence
The information in this article was obtained from the following sources:
- ↑ a b c d e f g h Mikhail V. Matz, Tamara M. Frank, N. Justin Marshall, Edith A. Widder, Sönke Johnsen: Giant Deep-Sea Protist Produces Bilaterian-like Traces In: Current Biology, Volume 18, 2008, pp. 1-6. doi : 10.1016 / j.cub.2008.10.028
- ↑ a b c d e f Andrew J. Gooday, Samuel S. Bowser, Brian J. Bett and Craig R. Smith: A large testate protist, Gromia sphaerica sp. nov. (Order Filosea), from the bathyal Arabian Sea , In: Deep Sea Research Part II: Topical Studies in Oceanography, Volume 47, 2000, pp. 55-73.
- ^ A b Ana Aranda da Silva, Jan Pawlowski, Andrew J. Gooday: High diversity of deep-sea Gromia from the Arabian Sea revealed by small subunit rDNA sequence analysis In: Marine Biology, Volume 148, 2006, pp. 769-777.
