View source for Biology:Occultammina

{{Short description|Genus of single-celled organisms}}
{{DISPLAYTITLE:''Occultammina''}}
{{Automatic taxobox
| image = Occultammina sp.png
| taxon = Occultammina
| authority = Tendal et al., 1982
| type_species = ''Occultammina profunda''
| type_species_authority = Tendal et al., 1982
| subdivision_ranks = 
| subdivision = 
}}

'''''Occultammina''''' is a [[Biology:Genus|genus]] of [[Biology:Xenophyophorea|xenophyophorea]]n [[Biology:Foraminifera|foraminifera]] known from the Atlantic and Pacific oceans. It is notable for being the first known infaunal xenophyophore as well as for being a possible identity for the enigmatic [[Biology:Trace fossil|trace fossil]] ''[[Unsolved:Paleodictyon|Paleodictyon]]''.

== Distribution and habitat ==
Like all other known xenophyophores, ''Occultammina'' is found in the deep ocean; the first known specimen was first discovered in 1980 at a depth of {{cvt|8,260|m}} in the [[Earth:Izu–Ogasawara Trench|Ogasawara Trench]], off the coast of Japan and described in 1982 by a joint research team from the [[Organization:University of Copenhagen|University of Copenhagen]] and the University of Tokyo.<ref name=":0">{{Cite journal|last1=Tendal|first1=Os|last2=Swinbanks|first2=Dd|last3=Shirayama|first3=Y.|date=1982-01-01|title=A new infaunal xenophyophore (xenophyophorea, protozoa) with notes on its ecology and possible trace fossil analogs|url=https://archimer.ifremer.fr/doc/00120/23170/|journal=Oceanologica Acta|volume=5|issue=3|pages=325–329|issn=0399-1784}}</ref> Further specimens referred to ''Occultammina'' sp. have been found at a depth of {{cvt|4,844|m}} in the Porcupine Abyssal Plain, in the North Atlantic.<ref name=":1">{{Cite journal|last=Levin|first=Lisa A.|date=February 1994|title=Paleoecology and Ecology of Xenophyophores|url=https://pubs.geoscienceworld.org/palaios/article/9/1/32-41/100347|journal=PALAIOS|volume=9|issue=1|pages=32–41|doi=10.2307/3515076|jstor=3515076}}</ref> Further studies have expanded its geographical and bathymetric range from {{convert|3,000|and|8,260|m}} in the Ogasawara Trench and from {{convert|4,500|to|4,800|m}} in the North Atlantic, and also recorded its presence at {{cvt|6,440|m}} in the [[Earth:Japan Trench|Japan trench]].<ref name=":1" /> ''Occultammina'' sp. has also been recovered at a depth of about {{convert|4050|metres}} near the [[Earth:Clipperton Fracture Zone|Clipperton Fracture Zone]], off the coast of western Mexico.<ref>{{Cite journal|date=2017-03-01|title=Giant protists (xenophyophores, Foraminifera) are exceptionally diverse in parts of the abyssal eastern Pacific licensed for polymetallic nodule exploration|journal=Biological Conservation|volume=207|pages=106–116|doi=10.1016/j.biocon.2017.01.006|issn=0006-3207|doi-access=free|last1=Gooday|first1=Andrew J.|last2=Holzmann|first2=Maria|last3=Caulle|first3=Clémence|last4=Goineau|first4=Aurélie|last5=Kamenskaya|first5=Olga|last6=Weber|first6=Alexandra A.-T.|last7=Pawlowski|first7=Jan}}</ref>

''Occultammina'' is infaunal; it typically is found at a depth of {{cvt|6|cm}} or less below the sediment's surface.<ref name=":1" /> It was the first known infaunal xenophyophore.<ref name=":2">{{Cite journal|last=Gooday|first=A. J.|date=1991-07-01|title=Xenophyophores (Protista, Rhizopoda) in box-core samples from the abyssal Northeast Atlantic Ocean, BIOTRANS area; their taxonomy, morphology, and ecology|url=http://dx.doi.org/10.2113/gsjfr.21.3.197|journal=The Journal of Foraminiferal Research|volume=21|issue=3|pages=197–212|doi=10.2113/gsjfr.21.3.197|issn=0096-1191}}</ref>

''Occultammina'' is found at [[Earth:Turbidite|turbidite]] facies in today's oceans.<ref name=":0" />

== Description ==
''Occultammina'' is an exceptionally large single-celled organism; like other xenophyophores it constructs a complex, single-chambered shell or "test" from sediment particles. It grows in a net-like shape, the test consisting of hollow tubes that branch or form loose polygons. It is typically flattened compared to other xenophyophores.<ref name=":0" /> It also has vertically ascending tubular outlets.<ref name=":1" /> ''Occultammina'' tubes are similar to those of ''Tendalia'' in general shape, though the test structure differs.<ref name=":3">{{Cite journal|last1=Gooday|first1=Andrew J.|last2=Holzmann|first2=Maria|last3=Goineau|first3=Aurélie|last4=Pearce|first4=Richard B.|last5=Voltski|first5=Ivan|last6=Weber|first6=Alexandra A.-T.|last7=Pawlowski|first7=Jan|date=2018-08-03|title=Five new species and two new genera of xenophyophores (Foraminifera: Rhizaria) from part of the abyssal equatorial Pacific licensed for polymetallic nodule exploration|url=https://academic.oup.com/zoolinnean/article/183/4/723/4757204|journal=Zoological Journal of the Linnean Society|volume=183|issue=4|pages=723–748|doi=10.1093/zoolinnean/zlx093|issn=0024-4082|doi-access=free}}</ref>

The test wall typically ranges from 70-120 μm in thickness; it is poorly cemented and consists of two layers. The outermost is 15-30 μm in thickness and composed primarily from clay; the inner layer is 50-90 μm thick and composed of silt and [[Biology:Radiolaria|radiolaria]]n tests. The interior of the test lining has between one and four ridges separating the stercomares, or waste masses.

Individual ''Occultammina'' tubes are between {{cvt|0.38|and|1|cm}} in diameter.<ref name=":0" /><ref name=":2" /> Networks of ''Occultammina'' sized {{cvt|5|–|10|cm}} across have been found at the Ogasawara trench.<ref name=":1" />

A specimen of ''Occultammina profunda'' was found to have unusually high levels of the radioactive isotopes [[Physics:Lead-210|lead-210]] (half-life 22.3 years), [[Physics:Polonium-210|polonium-210]] (half-life 138.376 days) and [[Physics:Radium-226|radium-226]] (half-life  1600 years), specifically in the grannelare and stercomare, among the highest levels of lead-210 recorded in any living organism. The authors suggest that the relative distribution of radionuclides in the organism's body parts implies that it grows and excretes comparatively rapidly.<ref>{{Cite journal|last1=Swinbanks|first1=David D.|last2=Shirayama|first2=Yoshihisa|date=March 1986|title=High levels of natural radionuclides in a deep-sea infaunal xenophyophore|url=http://www.nature.com/articles/320354a0|journal=Nature|volume=320|issue=6060|pages=354–358|doi=10.1038/320354a0|s2cid=4254138|issn=0028-0836}}</ref>

Unfortunately no DNA samples have been collected from ''Occultammina'', preventing further examination of its evolutionary relationships.<ref name=":3" />

== Relation to ''Paleodictyon'' ==
[[File:Paleodictyon P.San García Algeciras S03.JPG|thumb|The enigmatic fossil ''Paleodictyon'' has been likened to ''Occultammina'']]
The enigmatic "graphoglyptid" fossil ''Paleodictyon'' bears a passing resemblance to ''Occultammina'', and this has led to suggestions of relationship between the two. ''Paleodictyon'' fossils are known from sediments interpreted as representing abyssal paleoenvironments associated with turbidite deposits, potentially lending credence to the hypothesis. ''Paleodictyon'' also preserves vertically ascending tubules that have been likened to those of ''Occultammina''.

However, this relationship has been contested. The large size (up to {{cvt|0.5|m}}) of some ''Paleodictyon'' is unknown in modern ''Occultammina''; the regular hexagonal pattern of ''Paleodictyon'' is similarly not represented in ''Occultammina''. The apparent absence of collected sediment particles (known as xenophyae) in graphoglyptid fossils further casts doubt on the possibility.<ref name=":1" />

Modern examples of ''Paleodictyon'' have been discovered; however, they have not been able to clear up the issue. These specimens come from near the [[Earth:Mid-Atlantic Ridge|mid-Atlantic Ridge]] at a depth of {{convert|3,415|–|3,585|meters}}. The specimens ranged from {{cvt|2.4|to|7.5|cm}} in diameter. Dissection of one specimen did not reveal tubes, mucus, protoplasm, or evidence of a test. Staining of a second specimen did not reveal soft-bodied evidence for xenophyophores such as stercomares or granellae;  some small agglutinated fragments were found that could have been from a psamminid, but this is not unexpected in deep-sea sediments. DNA analysis also did not reveal evidence of xenophyophores in the sample. The modern samples also lacked the barium concentration caused by the barite crystals in xenophyophore tests. This study suggested that ''Paleodictyon'' could represent a burrow system or a [[Biology:Hexactinellid|glass sponge]].<ref>{{Cite journal|last1=Rona|first1=Peter A.|last2=Seilacher|first2=Adolf|last3=de Vargas|first3=Colomban|last4=Gooday|first4=Andrew J.|last5=Bernhard|first5=Joan M.|last6=Bowser|first6=Sam|last7=Vetriani|first7=Costantino|last8=Wirsen|first8=Carl O.|last9=Mullineaux|first9=Lauren|last10=Sherrell|first10=Robert|last11=Frederick Grassle|first11=J.|date=September 2009|title=Paleodictyon nodosum: A living fossil on the deep-sea floor|url=http://dx.doi.org/10.1016/j.dsr2.2009.05.015|journal=Deep Sea Research Part II: Topical Studies in Oceanography|volume=56|issue=19–20|pages=1700–1712|doi=10.1016/j.dsr2.2009.05.015|issn=0967-0645}}</ref>

== References ==
<references />

{{Taxonbar|from=Q23773166}}
[[Category:Foraminifera genera]]
[[Category:Monothalamea]]
[[Category:Xenophyophorea]]

{{Sourceattribution|Occultammina}}