Polysyncraton montanum, 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 : 2481-2482

Polysyncraton montanum sp. nov.

( figures 5B , 17C )

Distribution. Type locality: South Australia (Kangaroo I., Pissy Boy Rock between Snug Cove and Western River Cave on rock wall, 8–10 m, coll. K. Gowlett Holmes, holotype SAM E3224).

Description. In life the colony looks like a Leptoclinides , being a deep, slightly asymmetrical, mottled pink and white cone with a large terminal common cloacal aperture. The preserved colony is pinkish orange and the label is stained the same colour. The colony is smooth on the surface. Internally, bright orange zooids line the deep primary common cloacal canals surrounding test connectives to which the zooids are firmly attached, appearing to be in tight clumps. A thin superficial bladder cell layer is aspiculate but beneath that the spicules are crowded throughout. They are stellate, up to 0.08 mm diameter, with 9–11 conical pointed rays in optical transverse section.

Zooids have large thoraces with a broad flat-tipped atrial lip. A long tapering retractor muscle projects from the oesophageal neck. Gonads were not detected in the newly recorded specimens, and the number of stigmata could not be counted.

Remarks. The tropical P. pseudorugosum Monniot, 1993 (see Kott, 2001 and below) is not readily distinguished from the present species, having similar systems and spicules. However, it has a sheet-like colony with many common cloacal apertures rather than terminal ones like the present species. Other species of Polysyncraton with similar common cloacal systems and stellate spicules with 9–11 pointed conical rays are P. cuculliferum with smaller spicules (to 0.06 mm diameter) and P. sideris Kott, 2001 (with larger spicules to 0.14 mm diameter). The broad atrial lip resembles that of P. tegetum , but the spicule rays are never chisel-shaped. The colony is a similar colour to colonies of Didemnum fragum Kott, 2001 and has a similar terminal common cloacal aperture, but D. fragum has smaller zooids, lacks an atrial lip and has shorter spicule rays. The present species appears to be previously undescribed.

Polysyncraton pedunculatum Kott, 2001

Polysyncraton pedunculatum Kott, 2001: 121 (part, not specimen QM GH2387, Flinders I., pl. 6D~ P. rica ) and synonymy; 2004.

Distribution. Previously recorded (see Kott, 2001, 2004): South Australia (Great Australian Bight, Nuyts Archipelago, Yorke Peninsular, Investigator Strait). New record: South Australia (Kangaroo I., SAM E3230).

Description. The living colony is reddish tan, slightly translucent, biramous vertically ridged with a short, relatively narrow, basal stalk. Zooids are confined to the surface of the completely aspiculate colony. They are in irregular longish oval groups with primary common cloacal canals around each group. The test is soft and translucent.

Zooids have the usual long, fine retractor muscle projecting from about halfway down the oesophageal neck. Three coils of the vas deferens surround a number of testis follicles.

Remarks. Kott (2001) confused specimens of P. rica (which is only partially aspiculate with a smooth surface) with the present completely aspiculate, irregularly ridged species, which looks very different.

The report of four coils of the vas deferens (Kott, 2001) is incorrect. Reexamination of the material has shown that there are three coils in all specimens.

Figures

FIG. 5. (A–C) Polysyncraton longitubis (SAM E2929). (A) Surface of colony; (B) thorax; (C) abdomen. (D, E) Polysyncraton montanum (SAM E3224). (D) Thorax; (E) abdomen. Scale bars: 5.0 mm (A, C); 0.1 mm (B, D, E).

FIG. 17. (A) Polysyncraton galaxum (SAM E2927); (B) Polysyncraton longitubis (SAM E2929); (C) Polysyncraton montanum (SAM E3224); (D) Polysyncraton peristroma (QM G308608); (E) Polysyncraton pseudomagnetae (QM G308612); (F) Polysyncraton pseudorugosum (QM G308600); (G) Polysyncraton reticulum (SAM E2917); (H) Polysyncraton rica (SAM E3216).