Trididemnum sibogae (Hartmeyer, 1910)

Kott, Patricia, 2004, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part I), Journal of Natural History 38 (19), pp. 731-774 : 766-767

Trididemnum sibogae (Hartmeyer, 1910)

Didemnum sibogae Hartmeyer, 1910: 1489 .

Trididemnum sibogae: Kott, 2001: 283 and synonymy.

Distribution. New record: Victoria (Western Port, MV F68790 ). Previously recorded (see Kott, 2001): NW, southern and NE Australia.

Description. The colony is an encrusting sheet, and the ridges and furrows on the surface appear to be the result of an uneven substratum over which it was growing, although in places it is over-growing its own surface. There is an extensive posterior abdominal common cloacal cavity. Large stellate spicules (to 0.1 mm diameter and more) have 7–11 long, pointed rays in optical transverse section. An endostylar eye was not detected on the zooids.

Remarks. The species is distinguished from T. nobile by its larger spicules and longer more pointed rays, fewer vas deferens coils and four pairs of larval lateral ampullae.

Trididemnum lapidosum Kott, 2001 has similar spicules but lacks the extensive posterior abdominal cloacal cavities of the present species and is harder, with spicules crowded throughout. Trididemnum caelatum Kott, 2001 has three ectodermal ampullae and more spicule rays than the present species.