Lissoclinum scopulosum, Kott, 2004

Kott, Patricia, 2004, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part I), Journal of Natural History 38 (19), pp. 731-774 : 770-771

Lissoclinum scopulosum sp. nov.

( figure 21 )

Distribution. Type locality: Western Australia (NW Long I., Passage Is, coll. L. Marsh and S. Slack-Smith on RV Soela, 10 December 1979, holotype WAM 163.93).

Description. The colony is a hard, thin, sheet. Purple pigment in irregular particles forms a layer on the surface over the white spicules that crowd the remainder of the test. Pigment and spicules in the surface test are interrupted in a circle around the branchial apertures which are depressed into the colony in the preserved specimen. Common cloacal apertures are large and sessile. Spicules, moderately sized, to 0.05 mm diameter, have 9–11 club-shaped or slightly flattened tongue-shaped, or sometimes obelisk-like (square in section with conical tips) rays.

Zooids are stretched out and do not contract, the ventrum of each zooid adhering to the hard, rigid strip of test that crosses the thoracic common cloacal cavity. Long, rectangular stigmata, 11 in the anterior row of the branchial sac, are exposed directly to the cloacal cavity by a large, sessile atrial aperture. Neither the parietal body wall muscles nor a retractor muscle were detected, and the parietal body wall itself is withdrawn almost to the endostyle on each side.

Abdomina and embryos are embedded in the basal test. Testes are two-lobed. The sturdy larval trunk, 1.1 mm long, has the tail coiled halfway around it. Four rounded lateral ampullae are on each side of the three antero-median adhesive organs. Neither abdominal organs nor blastozooids were detected.

Remarks. This species, with its very hard, stony sheets, with a surface film of purple pigment, is also distinguished by its unusual spicules (some of which resemble some of the spicules in L. timorense ). Although they have different spicules from the present species, numbers of Lissoclinum spp. have their branchial apertures depressed into the colony leaving circular holes in the hard spicule-filled surface of the colony (see L. durabile Kott, 2001 and L. conchylium Kott, 2001 ).

Figures

FIG. 21. Lissoclinum scopulosum (WAM 163.93): (A) vertical section through colony; (B) zooid; (C) larva; (D) spicules. Scales: (A) 1.0 mm; (B, C) 0.2 mm.