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the web of life in southern Africa

Pyrosomella verticillata

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia > Chordata > Tunicata > Thaliacea > Pyrosomatida > Family: Pyrosomatidae > Genus: Pyrosomella


The zooids (individual filter-feeding animals with inhalent and exhalent siphons) are formed into small oval to oblong colonies up to 5 cm long and 3 cm in diameter, often flattened (van Soest 1981). The wall of the colony is transparent and colourless. Zooids are oval to slightly elongate in side view, up to 3.9 mm long.

Distribution and habitat

This pelagic species has an Indo-Pacific distribution that includes southern African seas: the distribution map for in van Soest (1981) shows three records from this region.


Pyrosomella verticillata like most members of the Pyrosomatidae is bioluminescent and colonies are able to light up for sustained periods. Each zooid in the colony has a pair of luminescent organs flanking the orals siphon. Light production may be the result of intracellular bioluminescent bacteria in the cells of these luminescent organs but this needs to be confirmed. Bowlby et al. (1990) showed how Pyrosomella verticillata and Pyrosoma atlanticum bioluminesce in response to light. If you shine light on zooids on the one side of the colony, they bioluminesce and their light stimulates adjacent individuals. In this way, the bioluminescence spreads over the colony from the point where the zooids were stimulated. A colony that lights up can in turn stimulate an adjacent colony to light up as well. At the same time as lighting up, the zooid closes its oral siphon and the cilia inside that cause the water flow, stop beating. Colonies are negatively buoyant so when water flow stops, the colony starts sinking slowly. It is thought that the ability to bioluminesce in response to light stimulation might be an adaptation to communicating about predators and by also closing the water flow and sinking, they can move to a depth where there are fewer predators (Bowlby et al. 1990).


  • Bowlby MR, Widder EA, Case JF. 1990. Patterns of stimulated bioluminescence in two pyrosomes (Tunicata: Pyrosomatidae). Biological Bulletin 179: 340-350.
  • van Soest RWM. 1981. A monograph of the order Pyrosomatida (Tunicata, Thaliacea). Journal of Plankton Research 3(4): 603631.

Text by Hamish Robertson