''Oikopleura'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small particles, down to the

nanoplankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

that includes (pelagic)

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

. Abandoned mucus houses sink to the deep, collecting organic particles during their descent. They make an important contribution to

marine snow In the deep ocean, marine snow (also known as "ocean dandruff") is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to ...

, since ''Oikopleura'' is abundant and is a very active filterer, using powerful strokes of its tail. Its abundance is less obvious from preserved samples (that are usually analyzed) because the gelatinous body disappears in the preservation process while leaving hardly any trace. Species of ''Oikopleura ''have the smallest genomes in the animal kingdom, only about 75 Mb. ''Oikopleura'' contains

bioluminescent Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorganisms including ...

species. About half of ''Oikopleura'' species are bioluminescent.

Taxonomy

* ''

Oikopleura (Coecaria) ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' , 1933 ** ''

Oikopleura (Coecaria) fusiformis ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Fol, 1872 *** ''Oikopleura (Coecaria) fusiformis cornutogastra'' Aida, 1907 ** ''

Oikopleura (Coecaria) gracilis ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1896 ** ''

Oikopleura (Coecaria) intermedia ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1896 ** ''

Oikopleura (Coecaria) longicauda ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' (Vogt, 1854) * ''

Oikopleura (Vexillaria) ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1933 ** '' Oikopleura (Vexillaria) albicans'' (Leuckart, 1853) ** ''

Oikopleura (Vexillaria) caudaornata ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' (Fenaux & Youngbluth, 1991) ** '' Oikopleura (Vexillaria) cophocerca'' (Gegenbaur, 1855) ** '' Oikopleura (Vexillaria) dioica'' Fol, 1872 ** ''

Oikopleura (Vexillaria) gaussica ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1905 ** ''

Oikopleura (Vexillaria) gorskyi ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Flood, 2000 ** ''

Oikopleura (Vexillaria) inflata ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' (Fenaux & Youngbluth, 1991) ** ''

Oikopleura (Vexillaria) labradoriensis ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1892 ** ''

Oikopleura (Vexillaria) parva ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohmann, 1896 ** ''

Oikopleura (Vexillaria) rufescens ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Fol, 1872 ** ''

Oikopleura (Vexillaria) vanhoeffeni ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Lohman, 1896 ** ''

Oikopleura (Vexillaria) villafrancae ''Oikopleura'' is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small par ...

'' Fenaux, 1992

Distribution

The oikopleurids are distributed in the tropical waters of all oceans and seas of the globe, having been reported widely in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

and the western coasts of the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

''Oikopleura dioica''

A species of particular interest under this genus is the ''

Oikopleura dioica ''Oikopleura dioica'' is a species of small pelagic tunicate found in the surface waters of most of the world's oceans. It is used as a model organism in research into developmental biology. Description ''Oikopleura dioica'' is a bioluminescent ...

'', which is an anomaly among

chordates A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five ...

. It has retained the fundamental body plan of the chordate; yet, it has lost the mechanism for

retinoic acid Retinoic acid (used simplified here for all-''trans''-retinoic acid) is a metabolite of vitamin A1 (all-''trans''-retinol) that mediates the functions of vitamin A1 required for growth and development. All-''trans''-retinoic acid is required in ...

signaling which operates during chordate development. The loss raises the question of the evolutionary constraints that have prevented similar changes in the other chordates. ''Oikopleura dioica''

hox gene Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the cor ...

s are distributed in nine locations around the genome whereas other

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fiv ...

s have a cluster of hox genes. Of note, this is the first chordate among the eukaryotes found to have

operon In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splic ...

References

External links

Integrated Taxonomic Information System (ITIS): ''Oikopleura'' Taxonomic Serial No.: 159668

National Center for Biotechnologu Information (NCFI): ''Oikopleura'' Taxonomy ID: 34763

''Oikopleura'' Genome Browser

Merriam-Webster: ''Oikopleura''

Videos

Youtube: Larvacea (''Oikopleura dioica'')

Photos

Flickr: Oikopleura sp. in the house
{{Taxonbar, from=Q3639186 Appendicularia Tunicate genera Bioluminescent animals