Didemnum, Savigny, 1816

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1192

Didemnum ? sp. 2

( Figure 18H )

Distribution

Record: Western Australia, CSIRO SS10/05 (Kalbarri, Stn 99, 252 m, 04.12.05, QM G328166).

Description

The colony is a flat sheet growing around a sponge with a colony of Polysyncraton pavementum . Stellate openings of the small zooids are evenly spaced over the upper surface. The surface layer of test overlying the shallow horizontal thoracic common cloacal cavity is thin. Spicules are crowded throughout the colony. They are small (to 0.03 mm diameter) and uniform, with 13–15 sturdy conical rays in optical transverse section with the wide bases of the rays crowded together toward the centre of the spicule. Zooids are small and mutilated and their structure is obscured.

Remarks

Didemnum jucundum Kott, 2001 , a temperate Australian species ranging across the southern coast of the continent from Esperance to Port Phillip Bay, has uniform stellate spicules similar to those of the present species, but they are very much larger.

The species has been provisionally assigned to the genus Didemnum on the basis of its small zooids and spicules and its simple horizontal common cloacal cavity. However, there is insufficient information to confidently assign this specimen to either genus or species.

Figures

Figure 18. Scanning electron micrographs of didemnid spicules: A, Didemnum multiampullae, QM G328057: B, Didemnum ossium, QM G328055; C, Didemnum perplexum, QM G328034; D, Didemnum plebeium, QM G328451; E, Didemnum tapetum, QM G328016; F, Didemnum velum, QM G328120; G, Didemnum sp 1, QM G328160; H, Didemnum sp. 2, QM G328166.