Pyrostremma spinosum (Giant fire salp)

[= Pyrosoma spinosum]

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

A massive, tubular colony of Pyrostremma spinosum photographed off Montague Island in NSW, Australia, close to the continental shelf in 25 meters of water, in 1985. [Photo by Mr Roger Fenwick , Victoria, Australia]

Description

Forms tubular colonies that can exceed 20 m in length! The open side of the tube is the posterior end (the common cloaca) and in a 10.2 m long colony, was measured at 1.2. m in diameter. It often has a very long tail projecting from the rim of the opening that can be as long as the colony. The colony tapers to the anterior end, which is  closed and pointed. The wall of the tube is made up of individual animals (zooids) that are embedded in a gelatinous test. The external surface of the test is covered with blunt, spine-like pyramids of fairly rigid jelly, with one pyramid next to the oral siphon of each zooid. These projections are about 5 mm apart and 2-3 mm high (Baker 1971). The oral (inhalent) siphon of each zooid is on the outside of the colony and the atrial (exhalent) siphon on the inside of the tube. The combined filtering of water from the outside to the inside of the tube by these thousands of zooids helps to keep the tube cylindrical in shape. It actually is quite fragile and if it is taken out of the water it collapses.

Zooids are up to 14.3 mm long, with the oral siphon 0.5 mm long and the cloacal siphon 5.2 mm long (van Soest 1981). Zooids of the other species in the genus, Pyrostremma agassizi, are only 8 - 10 mm long. The greater length of Pyrostremma spinosum zooids is mainly because of the long cloaca. 

Distribution and habitat

A pelagic species that occurs in all oceans from 40N to 45S (Van Soest 1981). The distribution map in Van Soest (1981) shows one record from southern African waters (well off the  east coast). The records of huge colonies of Pyrostremma spinosum are all from Australia and New Zealand (Griffin & Yaldwyn 1970; Baker 1971). I have found no records of similar sized individuals from southern African waters and marine biologists and divers that I have spoken to are unfamiliar with pyrosomatid colonies that reach these sizes in this region. Evidently the usual size of Pyrostremma spinosum colonies is about 20-50 cm long (Baker 1971) and so presumably it is these sized colonies that are more the norm in southern African waters.

As these colonies are very fragile, they can get broken up by surface waves. Observations of the larger colonies have been at depths below the level of strong wave action, to as deep as 40 m (Baker 1971).

Publications (by date)

  • Griffin DJG, Yaldwyn JC. 1970. Giant colonies of pelagic tunicates (Pyrosoma spinosum) from SE Australia and New Zealand. Nature 226: 464. doi:10.1038/226464a0
  • Baker AN. 1971. Pyrosoma spinosum Herdman, a giant pelagic tunicate new to New Zealand waters. Records of the Dominion Museum 7(12): 107-117.
  • Van Soest RWM. 1981. A monograph of the order Pyrosomatida (Tunicata, Thaliacea). Journal of Plankton Research 3(4): 603631.

Text by Hamish Robertson


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