Pyrosoma atlanticum

Pyrosoma atlanticum

''Pyrosoma atlanticum'' is a pelagic species of marine colonial tunicate in the class Thaliacea found in temperate waters worldwide. The name of the genus comes from the Greek words ''pyros'' meaning 'fire' and ''soma'' meaning 'body', referring to the bright bioluminescence sometimes emitted. The specific epithet ''atlanticum'' refers to the Atlantic Ocean, from where the first specimen of the species was collected for scientific description; it was described in 1804 by François Péron, a French naturalist.
Tunicates - Pyrosoma atlanticum This Pyrosoma atlanticum looks like a blotch of pinkish stuff but are a colony of tunicates. Mexico,Pyrosoma atlanticum,Socorro,Tunicates

Appearance

A colony of ''P. atlanticum'' is cylindrical and can grow up to 60 cm long and 4–6 cm wide. The constituent zooids form a rigid tube, which may be pale pink, yellowish, or bluish. One end of the tube is narrower and is closed, while the other is open and has a strong diaphragm. The outer surface or test is gelatinised and dimpled with backward-pointing, blunt processes. The individual zooids are up to 8.5 mm long and have a broad, rounded branchial sac with gill slits. Along the side of the branchial sac runs the endostyle, which produces mucus filters. Water is moved through the gill slits into the centre of the cylinder by cilia pulsating rhythmically. Plankton and other food particles are caught in mucus filters in the processes as the colony is propelled through the water. ''P. atlanticum'' is bioluminescent and can generate a brilliant blue-green light when stimulated.

Distribution

''P. atlanticum'' is found in temperate waters in all the world's oceans, usually between 50°N and 50°S. It is most plentiful at depths below 250 m . Colonies are pelagic and move through the water column. They undergo a large diurnal migration, rising toward the surface in the evening and descending around dawn. Large colonies may rise through a vertical distance of 760 m daily, and even small colonies a few millimetres long can cover vertical distances of 90 m .

Behavior

A study in the Indian Ocean comparing different zooplankton organisms found that colonies of ''P. atlanticum'' were the most efficient grazers of particles above 10 µm in diameter, catching a higher proportion of the particles than other grazers. This implies the species uses high biomass intake as a strategy, rather than investing in energy-conservation mechanisms.

Growth occurs by new rings of zooids being budded off around the edge of the elongating colony. A pair of luminescent organs is on either side of the inlet siphon of each zooid. When stimulated, these turn on and off, causing rhythmic flashing. No neural pathway runs between the zooids, but each responds to the light produced by other individuals, and even by light from other nearby colonies.

Habitat

''P. atlanticum'' is found in temperate waters in all the world's oceans, usually between 50°N and 50°S. It is most plentiful at depths below 250 m . Colonies are pelagic and move through the water column. They undergo a large diurnal migration, rising toward the surface in the evening and descending around dawn. Large colonies may rise through a vertical distance of 760 m daily, and even small colonies a few millimetres long can cover vertical distances of 90 m .Five specimens of the penaeid shrimp ''Funchalia'' were found living inside colonies of ''P. atlanticum''. Other amphipods also lived there, including the hyperiids ''Phronima'' and ''Phronimella'' spp.

Predators of ''P. atlanticum'' include various bony fishes, such as the spiky oreo, the big-eyed cardinalfish, and the pelagic butterfish, dolphins, and whales such as the sperm whale and giant beaked whale.

References:

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Taxonomy
KingdomAnimalia
DivisionChordata
ClassThaliacea
OrderPyrosomida
FamilyPyrosomidae
GenusPyrosoma
SpeciesP. atlanticum
Photographed in
Mexico