Lissoclinum stellatum, Kott, 2010

Kott, Patricia, 2010, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 2), Journal of Natural History 38 (26), pp. 2455-2526 : 2514-2515

Lissoclinum stellatum sp. nov.

( figures 13B , 21H )

Distribution. Type locality: Tasmania (Tasman Peninsula, Waterfall Bay, Dog Leg Cave on rock wall, 10–12 m, coll. K. Gowlett Holmes, 3 July 1998, holotype SAM E2926).

Description. The colony is sheet-like with brown pigment in the surface test intense around the large common cloacal canals. Crowded spicules are interrupted by oval vesicles in the basal and surface test. These vesicles appear as brown spots owing to the brown pigment in the test seen through these colourless, transparent vesicles. The ventrum of each thorax is embedded in the stand of solid test, which is surrounded by the deep primary common cloacal canals that extend the whole length of the zooid. The solid stands of test protrude slightly from the upper surface as rounded elevations. Common cloacal apertures are randomly distributed at the junctions of the circular common cloacal canals. The spicules are unique in this genus, usually stellate to 0.06 mm diameter with relatively few (five to seven) rays, often conical and pointed, but many with flat irregular or divided ray tips, and often the spicules are asymmetrical.

Zooids are narrow, with about 10 long, narrow stigmata in the anterior row, a wide open atrial aperture exposing the whole of the branchial sac to the common cloacal cavity, a retractor muscle projecting from halfway down the oesophageal neck, an undivided testis and a straight vas deferens. The thoraces are kept extended in the preserved specimens by the firm stand of solid test in which the ventrum is embedded.

Remarks. The common cloacal systems of the present species, like those of L. laneum and L. durabile Kott, 2001 , have zooids partially embedded along each side of primary common cloacal canals that surround solid stands of test, and although these common cloacal canals may be deep (the whole depth of the zooid) they are not posterior abdominal as they are in many species of this genus. Although L. laneum has an undivided testis like the present species, it is readily distinguished by the absence of spicules. Lissoclinum durabile has two testis follicles and burr-like spicules and also is readily distinguished. The form of the spicules is very unusual for this genus, similar ones being known only in Didemnum (e.g. D. complexum Kott, 2001 ), and the form of the common cloacal systems are also more often encountered in other genera such as Leptoclinides and Didemnum .

Figures

FIG. 13. (A) Lissoclinum laneum (SAM E2923), zooid with spherical and morula cells in the surrounding test. (B, C) Lissoclinum stellatum (SAM E2926). (B) Colony surface showing scattered spherical vesicles; (C) thorax. Scale bars: 0.1 mm (A, C); 2 mm (B).

FIG. 21. (A) Lissoclinum conchylium (QM G308632); (B) Lissoclinum diversum (WAM 140.93); (C) Lissoclinum durabile (SAM E3218); (D) Lissoclinum levitum (SAM E3219); (E) Lissoclinum ostrearium (SAM E3215); (F) Lissoclinum reginum (QM G308617); (G) Lissoclinum roseum (WAM 882.89); (H) Lissoclinum stellatum (SAM E2926).