Lissoclinum capsulatum, Kott, 2007

Kott, Patricia, 2007, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 4), Journal of Natural History 41 (17 - 20), pp. 1163-1211 : 1205-1206

Lissoclinum capsulatum sp. nov.

( Figures 5D , 11D )

Distribution

Type locality: Queensland (Northern Great Barrier Reef: 18.845 ° S, 146.795 ° E, 26.83 m, GBR Seabed Biodiversity Project sample 651, 25 September 2003, holotype QM G308804 ) .

Description

Clumps of four or five zooids, each enclosed in a white capsule of crowded spicules, are embedded in a thin, cloudy mucus-like sheet of delicate test. The cloudiness is caused by minute (to 0.1 mm diameter) spherical to irregular and sometimes granular cells with a slightly greenish tint. Spicules are stellate, to 0.05 mm diameter with up to 15 long pointed rays in optical section. Amongst these relatively small, regularly conical spicules are some with narrow, supplementary rays crowded between the longer stellate rays and some smaller, bilaterally symmetrical spicules (to 0.03 mm diameter) which have longer, conical rays at the apices of triangular or quadrate outlines and shorter central rays, consisting of needle-like rods.

The zooids have the usual large thorax, with the rim of the atrial aperture lacking an anterior lip, and often drawn back to expose the branchial sac directly to the common cloacal cavity. The gut forms an almost horizontal loop, bent ventrally behind the branchial sac. The testis is divided into two follicles and the straight vas deferens is expanded into a seminal vesicle at its proximal end where it lies between the two testis follicles. A single egg is in a brood pouch constricted off from the posterior end of the zooid.

Remarks

A few bilaterally symmetrical spicules with rays of unequal length like the majority of the spicules reported for L. pacificense (Kott, 1981) and L. taratara C. and F. Monniot, 1987 (see Kott 2004a) were detected in the present species but these are rare, and far outnumbered by the stellate spicules, which are almost unique in Lissoclinum , L. stellatum Kott, 2004b being the only other known species with similar (albeit fewer) conical rays. Both L. taratara and L. pacificense are also distinguished from the present species by their undivided testis and the former species is further distinguished in that its spicules do not encapsulate the zooids. Lissoclinum cornutum Monniot, 1992 from New Caledonia has large stellate spicules that distinguish it from the Australian species (see below), but also it has a number of testis follicles arranged in a circle like L. concaυum n. sp. from southern Australia and L. testiculatum ( Kott, 1983) from Port Essington. Divided male gonads also occur in L. conchylium Kott, 2001 , L. diυersum Kott, 2004b, and L. durabile Kott, 2001 , but these species all have burr-like rather than stellate spicules.

Embryos are brooded in a pouch constricted off from the posterior end of the abdomen also in L. caliginosum Kott, 2001 , L. calycis Monniot, 1992 , L. laneum Kott, 2004b , L. maculatum Kott, 2001 , and L. roseum Kott, 2001 , which also have burr-like spicules.

The minute spherical to irregular cells found scattered in the test that make it cloudy are known in the larval test of many species in this genus (see Kott 2001, p 294). Similar bodies also occur in the adult test of many Diplosoma species and some other species of Lissoclinum , e.g. L. laneum Kott, 2004b and L. multifidum ( Sluiter, 1909) (see Kott 2001). They do not appear to be symbiotic plant cells.

Zooids are encapsulated in burr-like rather than stellate spicules in L. roseum and L. punctatum . In L. pacificense , L. limosum , and L. calycis (in the ‘‘ υerrilli ’’ group: Kott 2001) the zooids are also encapsulated in spicules, although the spicules are bilaterally rather than radially symmetrical.

Figures

Figure 5. (A, B) Trididemnum nebula (QM G328001 syntype): (A) thorax; (B) larva. (C) Trididemnum titanium (QM G323351 holotype): colony. (D, E) Lissoclinum capsulatum (QM G308804 holotype): (D) thorax; (E) abdomen. Scale bars: 0.1 mm (A, B, D, E), 1 cm (C).

Figure 11. Scanning electron micrographs. (A) Trididemnum pigmentatum (QMG308842); (B) Trididemnum sibogae (QM G308893); (C) Trididemnum titanium (QM G308816); (D) Lissoclinum capsulatum (QM G308804); (E) Lissoclinum reginum (QM G308871); (F) Didemnidae?genus?species (QM G308889); (G, H) Didemnidae?genus?species [(G) QM G308888; (H) QM G308900].