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the web of life in southern Africa

Pyrosoma atlanticum

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

Description

Forms finger-shaped pink to yellowish pink colonies of zooids (each zooid is an individual animal with an inhalent and an exhalent siphon), measuring up to 60 cm long by 4-6 cm wide. Colonies upwards of 4 cm long can contain sexually mature zooids. The test on the exterior of the colony, which forms the matrix between the zooids, has numerous protuberences, up to 15 mm long, over the surface, each ending in a spine-like tip, although, rarely, the exterior can be smooth. The wall of the colony is opaque and tough, and the zooids are tightly packed. Zooids are rounded and up to 8.5 mm long.

Distribution and habitat

Regarded as the most widely spread and common pyrosomatid occurring in all oceans from 50ºN to 50ºS. There are numerous records from southern African seas (see distribution map in van Soest 1981).

Feeding

 

Bioluminescence

Pyrosoma atlanticum 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 Pyrosoma atlanticum and Pyrosomella verticillata 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).

Ecological interactions

  • Predators
    • fish. A variety of fish have been recorded preying on Pyrosoma atlanticum, but the records so far discovered are for species that are not native to southern African seas
    • birds, including:
      • Puffinus griseus (Sooty shearwater)
      • Thalassarche bulleri (Buller's albatross) (James & Stahl 2000). New Zealand study: 77% of samples contained Pyrosoma atlanticum, and this species made up 22% of the diet by weight. One individual had 69 specimens in its stomach. The largest specimen consumed was 14.3 cm in length.
    • cetaceans
    • turtles

Publications (by date)

  • Bowlby MR, Widder EA, Case JF. 1990. Patterns of stimulated bioluminescence in two pyrosomes (Tunicata: Pyrosomatidae). Biological Bulletin 179: 340-350.
  • Davenport J, Balazs GH. 1991. 'Fiery bodies' - are pyrosomas an important component of the diet of leatherback turtles? British Herpetological Society Bulletin 37: 33-38.

  • James GD, Stahl J-C. 2000. Diet of southern Buller's albatross (Diomedea bulleri bulleri) and the importance of fishery discards during chick rearing, New Zealand Journal of Marine and Freshwater Research, 34(3): 435-454. doi: 10.1080/00288330.2000.9516946

  • Cruz JB, Lalas C, Jillett JB, Kitson JC, Lyver PO'B, Imber M, Newman JE, Moller H. 2001. Prey spectrum of breeding sooty shearwaters (Puffinus griseus) in New Zealand. New Zealand Journal of Marine and Freshwater Research 35(4): 817-829. DOI:10.1080/00288330.2001.9517044
  • Lindley JA, Hernández F, Scatllar J, Docoito J. 2001. Funchalia sp. (Crustacea: Penaeidae) associated with Pyrosoma atlanticum (Thaliacea: Pyrosomatidae) off the Canary Islands. Journal of the Marine Biological Association UK 81: 173-174.
  • Lindsay DJ, Hunt JC, Hayashi K. 2001. Associations in the midwater zone: the penaeid shrimp Funchalia sagamiensis Fujino 1975 and pelagic tunicates (Order: Pyrosomatida). Marine and Freshwater Behaviour and Physiology, 34(3): 157-170.
  • Blanco C, Raduán MA, Raga JA. 2006. Diet of Risso's dolphin (Grampus griseus) in the western Mediterranean Sea. Scientia Marina 70(3): 407-411.
  • Perissinotto R, Mayzaud P, Nichols PD, Labat JP. 2007. Grazing by Pyrosoma atlanticum (Tunicata, Thaliacea) in the south Indian Ocean. Marine Ecology Progress Series 330: 1-11.
  • Frick MG, Williams KL, Bolten AB, Bjorndal KA, Martins HR. 2009. Foraging ecology of oceanic-stage loggerhead turtles Caretta caretta. Endangered Species Research 9: 91-97.

Text by Hamish Robertson