Didemnum crescente 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 : 1178-1179

Didemnum crescente Kott, 2001

( Figure 8B )

Didemnum crescente Kott 2001, p 166 ; 2004b, p 2491 and synonymy.

Distribution

Previously recorded (see Kott 2004b): South Australia ( Waterloo Bay ); Victoria (Mallacoota Inlet, Westernport); Tasmania (Triabunna) ; New South Wales (Eden). New record: Tasmania ( Bass Strait , QM G308815 ) .

Description

The colony has large thin branching vertical lamellae. It is red in preservative and the preservative is stained yellow. A superficial layer of bladder cells overlies crowded spicules that become less crowded in the central test. Spicules are stellate, to 0.06 mm diameter, with seven to nine robust conical rays in optical transverse section. Zooids are in clumps surrounded by deep primary common cloacal canals that project behind the zooids to isolate the outer zooidcontaining layer of the colony from the central test. The zooids have a long retractor muscle. Nine coils of the vas deferens surround the undivided testis. Larvae, in the central test, have a trunk 0.7 mm long, four pairs of lateral ampullae and a mass of yellow yolk.

Remarks

The species is distinguished from D. lissoclinum (which has similar spicules and larvae) by its nine coils of the vas deferens ( D. lissoclinum has only seven), superficial bladder cell layer, and the absence of crowded spicules in the central layer of test.

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).