Lissoclinum coactum, 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 : 2506-2508

Lissoclinum coactum sp. nov.

( figures 11 , 20H )

Distribution. Type locality: Western Australia (Five Mile Reef, about 10 km E of Hopetoun 33 ‡ 56’1 S, 120 ‡ 12’ E, 0–3 m, limestone reef, coll. L. Marsh, 13 January 1986, syntypes WAM 1136.89).

Description. Colonies are irregular flattened mats to 3–4 mm in maximum dimension. White-rimmed common cloacal apertures are evenly spaced about 5 mm apart on the upper surface. Between these, the surface is interrupted by evenly spaced stellate branchial apertures surrounded by a spicule-free circle of test depressed into the surface. The rim of the opening has clusters of spicules crowded in each lobe. Brown pigment is mixed with spicules in the surface test, forming a cream, relatively opaque surface layer. Spicules are also present, but not crowded through the remainder of the colony. Spicules, to 0.035 mm in diameter, are globular with 7–9 thick cylindrical flat-tipped rays in optical transverse section. The rays are formed of loosely bound parallel crystals.

Zooids are in clumps of six or seven in the test ligaments between the surface and the basal test. A short connective in which the abdomina are embedded anchors them to the relatively thick basal layer of test, but subdivides to separate the thoraces from one another. Brown stolonic vessels with large terminal vesicles are in the test and the brown pigment in the body wall of the zooids obscures their structure. The testis is divided into two follicles.

Remarks. These colonies are very soft with the consistency of the interior of Didemnum molle (Herdman, 1886) , a species with similar common cloacal systems, and a similar distribution of small globular spicules. The species are separated by the generic characters, differences in the shape of the colonies and in the presence of Prochloron in D. molle .

The present species is distinguished from most other Lissoclinum spp. by its relatively few and thicker spicule rays. Although there are a number of species in this genus with similar distribution of spicules, similar common cloacal cavities and similar zooids with the branchial apertures depressed into the surface of the colony (namely L. levitum Kott, 2001 , L. durabile Kott, 2001 , L. badium Kott, 2001 and L. reginum Kott, 2001 ), they all have more spicule rays. Also, L. levitum has stellate spicules and the others have burr-like ones rather than globular spicules of the present species. Lissoclinum durabile looks most like the present species, having evenly spaced common cloacal apertures on the upper surface and the same geographic range.

Lissoclinum vareau Monniot and Monniot, 1987 from French Polynesia appears to have spicules most like the present species although they have more rays, and the common cloacal systems differ, the tropical species having zooids embedded in the surface test rather than in ligaments crossing the common cloacal cavity.

Lissoclinum conchylium Kott, 2001

( figure 21A )

Lissoclinum conchylium Kott, 2001: 305 ; 2002c: 40.

Distribution. Previously recorded (see Kott, 2001, 2002c): Queensland (Heron I., Moreton Bay); Northern Territory (Darwin). New records: Northern Territory (Anglers Rock, QM G308613; South Shell I., QM G308632).

Description. Colonies are extensive, thin sheets, hard and brittle with crowded spicules, brownish beige in life and pinkish mauve to reddish brown in preservative. The pigment is confined to the surface layer of test, where reddish pigment cells are mixed with spicules, absent only from the area around the evenly distributed branchial openings. The common cloacal cavity is shallow and thoracic.

Spicules are small, to 0.04 mm diameter, burr-shaped with about 20 rod-like flatto round-tipped rays in optical transverse section. Common cloacal apertures are evenly distributed over the surface.

Zooids, embedded in the white test, are brown, with minute spherical brown cells in the haemocoel. The abdomen is bent up alongside the thorax. Nine stigmata are in the anterior row in the branchial sac, eight in the second and third

rows, and seven in the last row. The testis is divided into two follicles and the proximal end of the vas deferens, between the two follicles, is expanded into a seminal vesicle.

Remarks. The specimens differ from previously recorded material in their restricted common cloacal cavities with the abdomen entirely embedded rather than only partially embedded in the basal test as Kott (2001) reported. However, the spicules are identical to those previously described, as are the brown cells in

the haemocoel.

Figures

FIG. 11. Lissoclinum coactum (WAM 1136.89). (A) Colony surface; (B) vertical section through colony (semi-diagrammatic); (C) zooid. Scale bars: 1.0 cm (A); 0.5 mm (B); 0.1 mm (C).

FIG. 20. (A) Didemnum poecilomorpha (WAM 142.93); (B) Didemnum scopi (WAM 203.93); (C) Didemnum sordidum (WAM 189.93); (D) Didemnum spumante (WAM 194.90); (E) Didemnum tabulatum (WAM 143.93); (F) Didemnum ternerratum (SAM E2920); (G) Didemnum vahatuio (WAM 204.93); (H) Lissoclinum coactum (WAM 1136.89).

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).