Didemnum tabulatum Sluiter, 1909

Kott, Patricia, 2009, Taxonomic revision of Ascidiacea (Tunicata) from the upper continental slope off north-western Australia, Journal of Natural History 43 (31 - 32), pp. 1947-1986 : 1965

Didemnum tabulatum Sluiter, 1909

Didemnum tabulatum Sluiter, 1909, p. 49 . Kott 2001, p. 241.

Distribution

Previously recorded ( Kott 2001): western Australia (off Port Hedland); Indonesia. New record: CSIRO 05 / 07 western Australia ( Station 116: Broome, 16.75 S 121.05 E, 100 m, Sled tow, 30.6.07, QM G328566 ) .

Description

The colony is thin, closely attached to a rocky substrate and packed hard throughout with stellate spicules to 0.06 mm diameter with 15–19 short conical rays in optical transverse section. The zooids are of the usual form with a wide open, sessile atrial aperture. A short retractor muscle is present. Neither gonads nor details of the branchial sac were detected.

Remarks

The species has been assigned to the genus Didemnum mainly on the basis of the form of the zooid without the posteriorly orientated atrial siphon of Trididemnum or Leptoclinides , while the presence of the retractor muscle also excludes the latter genus.

Spicules are the same size as Polysyncraton millepore but have more rays, those of P. textus are similar but smaller than the present species while those of P. scobinum are similar but significantly larger and these Polysyncraton spp. have characteristic colonies that differ significantly from the thin encrusting ones of the present species. Didemnum astrum has similar spicules to those of the present species but it has fewer spicule rays and a surface layer of bladder cells. The present specimen is assigned to D. tabulatum mainly on the basis of its colony form and the form and size of its spicules and the general appearance of its zooids