| Pyrosoma atlanticum | |
|---|---|
 | |
| Pyrosoma atlanticum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Tunicata |
| Class: | Thaliacea |
| Order: | Pyrosomida |
| Family: | Pyrosomidae |
| Genus: | Pyrosoma |
| Species: | P. atlanticum |
| Binomial name | |
| Pyrosoma atlanticum Péron, 1804 [1] | |
| Synonyms[1] | |
Pyrosoma benthica Monniot & Monniot, 1966 | |
Pyrosoma atlanticum is a pelagic species of marine colonial tunicate in the class Thaliacea. It is 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 bioluminescent light sometimes emitted.[2] The specific name "atlanticum" refers to theAtlantic Ocean from where the species was first described in 1804 by the French naturalist, François Péron.[1]
[edit]Description
A colony of Pyrosoma atlanticum is cylindrical and can grow up to 60 cm (2 ft) long and 4-6 cm wide. The constituentzooids 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 (0.3 in) 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 process and the colony is propelled through the water at the same time. Pyrosoma atlanticum is bioluminescent and can generate a brilliant blue-green light when stimulated.[2][3]
[edit]Distribution and habitat
Pyrosoma 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 (800 ft).[4] Colonies are pelagic and move through the water column.[2] They undergo a large diurnal migration, rising towards the surface in the evening and descending around dawn. Large colonies may rise through a vertical distance of 760 metres (2,500 ft) daily and even small colonies a few millimetres long can cover vertical distances of 90 metres (300 ft).[5]
[edit]Biology
In a study in the Indian Ocean comparing different zooplankton organisms, it was found that colonies of Pyrosoma 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 that Pyrosoma atlanticum uses high biomass intake as a strategy rather than investing in energy conservation mechanisms.[6]
Growth occurs by new rings of zooids being budded off around the edge of the elongating colony. There are a pair of luminescent organs on either side of the inlet siphon of each zooid. When stimulated, these turn on and off, causing rhythmic flashing. There is no neural pathway between the zooids but each responds to the light produced by other individuals and even by light from other nearby colonies.[7]
[edit]Ecology
Five specimens of the penaeid shrimp Funchalia were found living inside colonies of Pyrosoma atlanticum. Other amphipods also lived there including the hyperiidsPhronima and Phronimella spp.[8]
Predators of Pyrosoma atlanticum include various bony fish such as the spiky oreo, the big-eyed cardinalfish and the pelagic butterfish, dolphins and whales.[4]
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