Gromia sphaerica

{{Short description|Species of single-celled organism}}

{{Speciesbox

| image = Gromia in situ closeup.png

| image_caption = Close-up of Gromia in place. Note the particles of sand and muck stuck to the surface.

| genus = Gromia

| species = sphaerica

| authority = Gooday, Bowser, Bett & Smith 2000

}}

Gromia sphaerica is a large spherical testate amoeba, a single-celled eukaryotic organism and the largest of its genus, Gromia. The genus itself contains about 13 known species, 3 of which were discovered as late as 2005.{{cite journal|doi=10.1111/j.1096-3642.2009.00540.x |doi-access=free |title=Three new species of deep-sea Gromia (Protista, Rhizaria) from the bathyal and abyssal Weddell Sea, Antarctica |year=2009 |last1=Rothe |first1=Nina |last2=Gooday |first2=Andrew J. |last3=Cedhagen |first3=Tomas |last4=Fahrni |first4=José |last5=Hughes |first5=J. Alan |last6=Page |first6=Anton |last7=Pearce |first7=Richard B. |last8=Pawlowski |first8=JAN |journal=Zoological Journal of the Linnean Society |volume=157 |issue=3 |pages=451–469 }} It was discovered in 2000, along the Oman margin of the Arabian Sea, at depths around {{convert|1163|to|1194|m|ft|sp=us}}. Specimens range in size from {{convert|4.7|to|38|mm|in|abbr=off|sp=us}} in diameter. The test (organic shell) is usually spherical in shape and honeycombed with pores. There are filaments on the bottom of the organism, where it is in contact with the seafloor, and it is mostly filled with stercomata (waste pellets).{{cite journal |last1=Gooday |first1=Andrew J |last2=Bowser |first2=Samuel S |last3=Bett |first3=Brian J |last4=Smith |first4=Craig R |title=A large testate protist, Gromia sphaerica sp. nov. (Order Filosea), from the bathyal Arabian Sea |journal=Deep Sea Research Part II: Topical Studies in Oceanography |date=January 2000 |volume=47 |issue=1–2 |pages=55–73 |doi=10.1016/S0967-0645(99)00100-9 |bibcode=2000DSRII..47...55G |url=http://cat.inist.fr/?aModele=afficheN&cpsidt=1248817 |via=Centre National de la Recherche Scientifique |access-date=2008-11-20 |archive-date=2012-05-31 |archive-url=https://web.archive.org/web/20120531131638/http://cat.inist.fr/?aModele=afficheN&cpsidt=1248817 |url-status=dead |url-access=subscription }}

In 2008, {{convert|30|mm|in|abbr=off|sp=us|adj=on}} specimens were found off the coast of Little San Salvador in the Bahamas by researchers from the University of Texas. These Gromia were discovered to make mud trails as much as {{convert|50|cm|in|abbr=off|sp=us}} in length. It was previously thought that single-celled organisms were incapable of making these kinds of trails, and their cause was previously a source of speculation. The mud trails made by the Bahamian Gromia appear to match prehistoric mud trails from the Precambrian, including 1.8 billion year-old fossil trails in the Stirling formation in Australia.{{cite journal| last = Matz | first = Mikhail V. | author2 = Tamara M. Frank | author3 = N. Justin Marshall | author4 = Edith A. Widder | author5 = Sonke Johnsen | title = Giant Deep-Sea Protist Produces Bilaterian-like Traces | journal = Current Biology | volume = 18| issue = 23 | pages = 1849–1854 | publisher = Elsevier Ltd | date = 2008-12-09 | url = http://www.biology.duke.edu/johnsenlab/pdfs/pubs/sea%20grapes%202008.pdf | doi = 10.1016/j.cub.2008.10.028 | access-date = 2008-12-05 | pmid = 19026540| s2cid = 8819675 | doi-access = free }}{{cite news | last = Reilly | first = Michael | title = Single-celled giant upends early evolution | publisher = NBC News | date = 2008-11-20 | url = https://www.nbcnews.com/id/wbna27827279 | access-date = 2008-12-05}}{{cite news |url=https://cns.utexas.edu/news/giant-protist |publisher=University of Texas at Austin College of Natural Sciences |title=Discovery of Giant Roaming Deep Sea Protist Provides New Perspective on Animal Evolution |date=2008-11-20 |access-date=2019-07-21 |archive-date=2019-07-21 |archive-url=https://web.archive.org/web/20190721221950/https://cns.utexas.edu/news/giant-protist |url-status=dead }}{{cite news |title=Rolling 'Sea Grape' Rocks The Fossil Record |url=https://www.sciencedaily.com/releases/2008/12/081203190030.htm |access-date=2018-07-24 |work=ScienceDaily |date=2008-12-04 |language=en}} Because the tracks of Gromia resemble the 1.8 billion year old traces that were believed to represent the traces of complex bilaterian worms, said tracks could have been a result of similarly giant single-celled organisms instead of complex animals.