Leptoclinides dubius ( Sluiter, 1909 )

Kott, Patricia, 2005, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3), Journal of Natural History 39 (26), pp. 2409-2479 : 2418-2419

Leptoclinides dubius ( Sluiter, 1909)

( Figure 14B )

Polysyncraton dubium Sluiter 1909, p 69 .

Leptoclinides dubius: Kott 2001, p 54 and synonymy; 2004a, p 734; 2004c, p 40.

Distribution

Previously recorded (see Kott 2001, 2004a, 2004c): Western Australia (Houtman’s Abrolhos); Queensland (Great Barrier Reef, Whitsunday Is, Bowen, Lizard I.); Northern Territory (Darwin); Indonesia, Philippines, New Caledonia. New records: Western Australia (off Port Hedland, 165.90; Shark Bay, WAM 1093.89; Cockburn Sound, WAM 136.93).

Description

Smooth-surfaced colonies, with an extensive posterior abdominal cavity, encrusting weed. Although a variety of colours have been recorded for the living colonies (see Kott 2001), the newly recorded one from Darwin (QM G 308728) is pink with white markings identical with specimens from the southern and central Great Barrier Reef ( Kott 2001, Plate 2G, H). The newly recorded colony from Cockburn Sound is soft and translucent, growing around debris (mud, worm tubes) which is embedded in the central test core and has sparse spicules in the surface test. In the other specimens the usual layer of small crowded spicules is at the surface. A single and less crowded layer is always on the base of the colony and spicules are sparse elsewhere. They are burr-like, to 0.03 mm diameter and diverse, having rod-like, fusiform or slate-pencil urchin or club-shaped rays previously described. Except when spicules are sparse in the superficial layer of test, a single layer is in the test lining the urn-shaped branchial siphon and they outline the margins of the stellate branchial apertures. Branchial siphons are constricted at the base where there is a false siphon. Fourteen stigmata are in the anterior row on one side of the branchial sac. The gut forms a double loop in the specimens from Shark Bay and Cockburn Sound, which have about 14 male follicles in the grape-like three-dimensional mass. Specimens from Port Hedland are immature, and as well as lacking gonads, the gut forms a straight vertical loop rather than the double loop characteristic of the mature specimens of this species.

Remarks

This species is readily characterized by its small, diverse spicules in a thin layer at the surface and on the base of the colony, the false siphon at the base of the branchial siphon, the double gut loop, the grape-like mass of testis follicles and the S-shaped course of the vas deferens. Usually this species has spicules crowded in the surface of the test, and their restricted distribution in the colony from Cockburn Sound could have resulted from its location at the southern extremity of the species’ geographic range. The zooid has the usual species characters. Its urn-shaped branchial siphon, recorded previously for L. durus Kott, 2001 , is a common characteristic of the dubius species group (see Kott 2001).

Figures

Figure 14. Scanning electron micrographs of the calcareous spicules of: (A) Leptoclinides decoratus (SAM E3257); (B) Leptoclinides dubius (WAM 1093.89); (C) Leptoclinides frustus sp. nov. (SAM E3255, holotype); (D) Leptoclinides kingi (WAM Z20557); (E) Leptoclinides minimus sp. nov. (WAM 30.84, holotype); (F) Leptoclinides pulvinus sp. nov. (QM G308742, holotype); (G) Polysyncraton galaxum (SAM E3250); (H) Polysyncraton glaucum (QM G308736).