Lissoclinum patella ( Gottschaldt, 1898 )

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 : 769-770

Lissoclinum patella ( Gottschaldt, 1898)

( figure 20D )

Didemnoides patella Gottschaldt, 1898: 315 .

Lissoclinum patella: Kott, 2001: 315 and synonymy; Monniot and Monniot, 1996: 174; Monniot and Monniot, 2001: 285 .

Diplosomoides tropicum Sluiter, 1909: 88 .

Distribution. Previously recorded (see Kott, 2001): Indo-West Pacific from the western Indian Ocean in the west to French Polynesia in the east.

Description. The holotype of Didemnoides tropicum Sluiter, 1909 (ZMA TU 500) has been examined. It is a robust slab with the usual aspicular basal layer of test, which varies in thickness, probably accommodating irregularities in the substratum. Ridges of aspicular test on the surface isolate flat depressions into which the zooids open. The surface ridges are relatively low for this species and the depressions are wider and more open. As usual spicules are confined to the middle zooid layer. As previously reported, the globular spicules vary greatly in size and although the maximum size recorded previously was 0.08 mm diameter, one of 0.11 mm diameter was found in the newly examined specimen. Prochloron is in the common cloacal cavity in the middle (zooid) layer of the colony.

Zooids are as previously described for this species, having a long branchial siphon with a false siphon at the base. The branchial siphons penetrate the thick surface bladder cell layer. The oesophageal neck is long; a short post-pyloric part of the gut loop is bent ventrally, testis is undivided and the vas deferens is straight.

Remarks. The report of two testis follicles in Diplosomoides tropicum ( Sluiter, 1909) obscured its similarity to the present species. However, on re-examination of the holotype of D. tropicum the testis is found to be entire, and Sluiter’s report of two lobes could not be confirmed. Lissoclinum cerebrale ( Michaelsen, 1920) from Zanzibar also has a colony similar to L. patella with circular or elongate pits in the surface (containing the openings of the branchial siphons) between broad, high anastomosing gelatinous ridges of test. Spicules are in the zooid layer in the centre of the colony and zooids have an undivided testis with a straight duct. However, the spicules are not spherical like those of L. patella , but are bilaterally symmetrical and dumb-bell shaped ( Michaelsen, 1920: pl. 1, figure 4 ).

Figures

FIG. 20. Lissoclinum levitum (SAM E3204): (A) abdomen; (B) spicules. Lissoclinum pacificense (QM G300973): (C) spicules. Lissoclinum patella (ZMA TU500): (D) spicules. Scale: (A) 0.1 mm.

FIG. 4. Polysyncraton linere (MV F70228): (A) thorax; (B) abdomen; (C) larva; (D) spicules. Scales: (A–C) 0.1 mm.