''Pyrosomella verticillata'', the fire salp, is a species of colonial

pyrosome Pyrosomes are free-floating colonial tunicates in family Pyrosomatidae. Pyrosomes consist of colonies of small Zooids. There are three genera, '' Pyrosoma'', '' Pyrosomella'' and '' Pyrostremma'', and eight species. They usually live in the uppe ...

with an Indo-Pacific distribution.

Description

An individual ''P. verticillata''

zooid A zooid or zoöid is an animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zooids can ...

is typically about 4 mm long, while colonies are up to 5 cm long and 3 cm in diameter, and oval to oblong in shape. The wall of the colony is transparent and colorless.

Distribution

The species occurs in the warm Indo-Pacific and from the

Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...

to Japan, and has also been reported from the southwest Atlantic off Rio de Janeiro.

Bioluminescence

The species is

bioluminescent Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...

, with each zooid possessing a pair of luminescent organs next to the oral siphon, within which light production is probably carried out by symbiotic bacteria. Colonies respond to incoming light (e.g. artificial stimulation) by lighting up, and this phenomenon spreads among adjacent zooids until the entire colony is lit up; this may spread to adjacent colonies. Colonies may sustain light emission for extended time periods. Light emission is accompanied with cessation of

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

motion in zooids' oral siphons, causing colonies to start sinking in the water column. This combined bioluminescence and descent behavior has been interpreted as a technique for avoiding predation.

References

{{Taxonbar, from=Q4923336 Pyrosomatidae Animals described in 1909