Lissoclinum diversum, 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 : 2508-2510

Lissoclinum diversum sp. nov.

( figures 12 , 21B )

Distribution. Type locality: Western Australia (NE end of Kendrew I. Dampier Archipelago, under boulders, reef flat, coll. L. Marsh Crown of Thorns Survey, 10 October 1972, holotype WAM 140.93).

Description. Colonies are hard, encrusting sheets, the stellate branchial apertures depressed into an otherwise smooth, even surface. The common cloacal cavity is thoracic, and the surface test is connected to the thicker basal test by

firm cylindrical columns each surrounded by six or seven thoraces with their ventral surfaces embedded in the test of these connectives. These firm columns of test crossing the common cloacal cavity contribute to the firmness of the colony. Abdomina are embedded in the basal test. The relatively small (to 0.0375 diameter) spicules are crowded throughout the test, also contributing to the hardness of the colony. They are globular to burr-like, with 11–17 rod-like

to club-shaped rays in optical transverse section, and sometimes flattened to concave tips of the rod-like cylindrical rays appear to have small rounded to conical tips contained in them.

The large thoraces have a large sessile atrial aperture exposing most of the branchial sac directly to the common cloacal cavity. Ten long rectangular stigmata are in the anterior row of the branchial sac, nine in the second, eight in the third and seven in the last row. A retractor muscle was not detected. The

proximal end of the vas deferens, where it forms between the two testis follicles, is expanded into a seminal vesicle, narrowing as it extends anteriorly.

Remarks. Lissoclinum timorense ( Sluiter, 1909) has similar spicules of about the same size, but an undivided testis, a three-dimensional common cloacal cavity and slit-like branchial apertures. Further, the symbiotic green cells of L. timorense have not been detected in the present species. Lissoclinum conchylium Kott, 2001 has similar zooids with stellate apertures depressed into the upper surface and two testis follicles like the present species, but its spicules are larger and less diverse with more rays, and clumps of abdomina project up into the floor of the more spacious common cloacal cavity. Lissoclinum reginum Kott, 2001 has brown cells in the haemocoel, an atrial lip and more numerous spicule rays which distinguish it from the present species.

Lissoclinum durabile Kott, 2001

( figure 21C )

Lissoclinum durabile Kott, 2001: 306 and synonymy; 2002c: 41; 2004.

Distribution. Previously recorded (see Kott, 2001, 2002c, 2004): Western Australia (Esperance), South Australia (West I., Wright I.), Victoria (Western Port), New South Wales (Coffs Harbour), Northern Territory (Darwin). New records: South Australia (Kangaroo I., SAM E3217-8).

Description. Common cloacal apertures are on short, wide, rigid cylindrical, chimney-like protrusions about 0.5–1.0 cm apart on the surface of the yellowish white colonies. The whole or at least the basal part of these protrusions is bluish purple, while at least the rim of the opening, but sometimes as much as the upper half of the protrusion is white. Irregular bands of the blue pigment radiate out from the base of the cylindrical protrusions across the surface of the colony. This blue/purple pigment is paler in the smaller colonies (SAM E3217). Branchial apertures, with a thin layer of spicules in the siphon lining, are in a circle of thin spicule-free test depressed into the surface of the colony, each depression sharply defined by a white ring of crowded spicules in the test surrounding it. The colony is brittle, spicules being crowded throughout and readily falling out of the test when it is torn. The common cloacal cavity is an extensive horizontal space at thorax level, thoraces crossing it adhering tightly to separate ventral strips or to connectives shared by two to four zooids. Abdomina sometimes are embedded in the relatively thin basal test although in other specimens they project up into the common cloacal cavity. Spicules are usually burr-shaped, to 0.04 mm diameter, with relatively thick, almost club-shaped rays, although a few are stellate with about nine broad rays in optical transverse section.

Zooids are conspicuous in the preserved material, with dark cells in the haemocoel. The atrial apertures expose most of the branchial sac to the common cloacal cavity, the sides of the aperture being drawn ventrally almost to the endostyle. Thoraces are large with 10 stigmata in the anterior row and a large circular lateral organ opposite the middle interstigmatal vessel on each side of the endostyle.

Remarks. This is a readily identified species, with characteristic wide-open common cloacal apertures protruding from the surface and an unusual and conspicuous colour pattern that varies only in the intensity of the colour. It has an extensive range across the southern Australian coast and, although at present it has not been recorded either from the western Australian coast, or from the north-eastern coast north of New South Wales, it is recorded from Darwin and it may be found to be present around the whole of the continent.

Figures

FIG. 12. Lissoclinum diversum (WAM 140.93). (A) Vertical section through colony (semidiagrammatic); (B) thorax; (C) abdomen. Scale bars: 1.0 mm (A); 0.1 mm (B, C).

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).