Leptoclinides fluxus, 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 : 1169

Leptoclinides fluxus sp. nov.

( Figures 1B, C , 6E )

Distribution

Type locality: Great Barrier Reef (GBR Seabed Biodiversity Project SBD 504333 sample 816, 17.865 ° S, 146.645 ° E, 66 m, 26 September 2003, holotype QM G308817 ) .

Description

The holotype colony is a firm sheet encrusting pebbles. White bands are in the surface test where spicules at branchial siphon level are crowded over the deeper common cloacal canals. These surround translucent areas where patches of spherical to irregular black pigment cells are mixed with a superficial layer of bladder cells to create a marbled pattern on the surface test. Dark pigment also surrounds some of the zooids. Branchial apertures open to the surface in these translucent areas and a group of three spicules is in the siphonal lining of each aperture. Spicules are chrysanthemum-like, to 0.05 mm diameter, with long, straight rod-like rays, about 15–17 in optical transverse section. The few common cloacal apertures at the junction of some of the canals are sessile with black pigment around the rims. As well as the crowded spicules over the primary common cloacal canals, a less crowded layer is at zooid level but they are only sparse elsewhere.

Zooids are robust with a relatively long branchial siphon, a large, square branchial sac with eight or nine stigmata per row, and a posteriorly orientated atrial siphon. As in all Leptoclinides spp. the zooids lack a retractor muscle. Oesophageal buds are present, each with four rows of stigmata. Gonads were not detected.

Remarks

Despite the lack of gonads, the present colony is assigned to the genus Leptoclinides on the basis of its robust zooids, posteriorly orientated atrial siphon and lack of a retractor muscle.

The colony is unusual in having crowded spicules forming a white opaque band over the common cloacal canals and less crowded spicules around the clumps of zooids where the test is more translucent. The spicules also are unusual, resembling some in the genus Lissoclinum . In Leptoclinides , L. leυitatus Kott, 2001, recorded from northeastern and northwestern Australia and the Northern Territory (see Kott 2004b), is the only known species with spicules of similar size and numbers of rays, although the latter are long pointed cones rather than the rod-like rays of the present species. Kott (2005a), in discussing the relationship of L. leυitatus and L. echinus Kott, 2001 , distinguished the former species by the presence of some smaller burr-shaped spicules, although their spicules are more readily distinguished by the fewer rays in those of the latter species.

Figures

Figure 1. (A) Atriolum irregulare (QM G323245 holotype): larva. (B, C) Leptoclinides fluxus (QM G308817 holotype): (B) colony surface; (C) zooid. (D–F) Polysyncraton gratum (QM G308891): (D) thorax; (E) abdomen; (F) larva. (G) Polysyncraton reticulum (QM G323330): larva. Scale bars: 0.1 mm (A, C–G); 1 mm (B).

Figure 6. Scanning electron micrographs. (A) Atriolum irregulare (QM G323245); (B) Leptoclinides albamaculatus (QM G308876); (C) Leptoclinides dubius (QM G308892); (D) Leptoclinides durus (QM G308894); (E) Leptoclinides fluxus (QM G308817); (F) Leptoclinides placidus (QM G308766); (G) Polysyncraton cuculliferum (QM G3088458); (H) Polysyncraton gratum (QM G308891).