Didemnum lissoclinum Kott, 2001

Kott, Patricia, 2007, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 4), Journal of Natural History 41 (17 - 20), pp. 1163-1211 : 1183

Didemnum lissoclinum Kott, 2001

( Figure 8G )

Didemnum lissoclinum Kott 2001, p 2496 and synonymy; 2004b, p 2496.

Distribution

Previously recorded (see Kott 2004b): South Australia (Great Australian Bight, Yorke Peninsula, Gulf St. Vincent, Kangaroo I.); Victoria (Mallacoota Inlet, Deal I.); New South Wales (Jervis Bay, Port Hacking). New records: Tasmania (Bass Strait, QM G308813–4).

Description

Large, upright, branching colonies, a whitish colour in preservative. Spicules are crowded in the surface test. In some places small spicule-filled papillae are crowded on the surface. Spicules also are crowded in the central test to form a stiff supporting skeleton. Spicules are stellate, to 0.07 mm diameter, with seven to nine sturdy pointed rays.

Zooids are in clumps, each clump surrounded by the deep primary cloacal spaces that separate them from the central test. Gonads were not detected in the present specimens. Larvae, present in the central test, have a trunk 0.7 mm long, with the tail wound threequarters of the way around it. Four lateral ampullae are along each side of the anteromedian adhesive organs.

Remarks

Although it has similar vertical colonies, the species differs from D. fragum in having crowded spicules forming a skeleton in the central test (as in Trididemnum amiculum ) and in its fewer spicule rays (9–11 in optical transverse section in D. fragum ). Also, the larvae of D. fragum have six pairs of lateral ampullae and the eggs are large and yellow. Didemnum crescente Kott, 2001 has similar spicules and a similar larva to the present species, but its larvae are yellow, it has a superficial layer of bladder cells, its spicules are less crowded in the central core of test (as in D. fragum ) and the preservative is stained yellow. Although the testes have not been detected in the newly recorded colony, seven coils of the vas deferens have been reported ( Kott 2001) while D. crescente has nine.

Figures

Figure 8. Scanning electron micrographs. (A) Didemnum coralliforme (QM G308861); (B) Didemnum crescente (QM G308815); (C) Didemnum fragum (QM G308826); (D) Didemnum grande (QM G308867); (E) Didemnum granulatum (QM G308843); (F) Didemnum jedanense (QM G308846); (G) Didemnum lissoclinum (QM G308814); (H) Didemnum mantile (QM G308887).