Polycarpa argentata ( Sluiter, 1890 )

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 : 1199

Polycarpa argentata ( Sluiter, 1890)

Styela argentata Sluiter 1890, p. 340 . Kott 1985, p. 148 and synonymy.

Distribution

Previously recorded (see Kott 1985); Western Australia (Rowley Shoals); Queensland (Moreton Bay, Heron I., Britomart Reef, Cape Kimberley, Lizard I.); Indonesia, Palau Is, Gilbert I., Marshall Is. New record: Western Australia CSIRO SS10/05 (Point Hillier, Stn 21, 97 m, 21.11.05, QM G328450).

The present record is the most southerly for this Indo-western Pacific tropical species.

Description

The specimen is large, 11 cm long, very rough and wrinkled and both apertures are tightly closed. The branchial aperture is turned dorsally and the atrial aperture is directed anterodorsally. The test is tough with sand embedded in it, the body wall is muscular and relatively thin and both the short siphons are darkly coloured. The dorsal tubercle has a relatively open convoluted slit. Four narrow branchial folds are separated by wide expanses of flat branchial sac. The terminal part of the gut loop gut forms a tight circular loop around a flat-topped, circular endocarp before turning anteriorly into a long, straight rectum that terminates near the atrial opening in an anus that is fringed with small, rounded scallops. Very numerous small comma-shaped polycarps, the pointed end directed dorsally, overlap one another in the basal half of each side of the body. There are no other endocarps on the body wall.

Remarks

The newly recorded specimen is very like the one figured by Kott (1985, Figure 66a). Internally the circular curve of the gut loop, the anal border and the polycarps are also similar. Differences between the newly recorded specimen and the smaller ones figured by Kott are the longer rectum, larger dorsal tubercle and the more numerous overlapping polycarps in the present specimen.