Didemnum perplexum Kott, 2001

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 : 1187-1188

Didemnum perplexum Kott, 2001

( Figure 18C )

Didemnum perplexum Kott 2001, p. 224 ; 2004a, p. 757 and synonymy.

Distribution

Previously recorded (see Kott 2004a): Queensland (Great Barrier Reef); New Caledonia; Indonesia. New record: Western Australia CSIRO SS10/05 (Bald I., Stn 35, 157 m, 24.11.05, QM G328122; Kalbarri, Stn 102, 96 m, 05.12.05, QM G328034).

The new record extends the known range of the present species from the tropical West Pacific including the Great Barrier Reef to the tropical waters of Western Australia and the Indian Ocean .

Description

The newly recorded colonies are the usual thin, brittle sheet-like encrusting forms previously described for this species. Minute spicule-filled papillae are on parts of the surface. Stellate spicules to 0.046 mm diameter with seven to nine and occasionally only five relatively long, strong conical rays in optical transverse section are present throughout the colony. A vast horizontal common cloacal cavity is present at thorax level. Zooids are small, sometimes narrow, fusiform and brownish red in preservative. A long, tapering retractor muscle projects into the test from about halfway down the long oesophageal neck. The testis is undivided and is surrounded by seven coils of the vas deferens. Larvae, with the trunk 0.8 mm long and the tail wound almost the whole way around it, have six ampullae along each side of the three antero-median adhesive organs.

Remarks

The spicules have conspicuously conical rays that contrast with the more cylindrical shapes of so many Didemnum spp. spicule rays, such as D. candidum , D. stragulum and D. delectum . Didemnum incanum ( Herdman, 1899) has similar but smaller spicules.

Didemnum granulatum Tokioka, 1954 has similar but larger spicules (to 0.06 mm) and the larval trunk is significantly smaller with only four pairs of lateral ampullae.

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.