Didemnum asterix, Kott, 2004

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 : 747-748

Didemnum asterix sp. nov.

( figure 8D )

Distribution. Type locality: Western Australia (9 n. mls north of Cape Legendre, 42– 40 m, coll. L. Marsh and M. Besant on RV Soela, 28 September 1982, holotype WAM 633.88).

Description. The colony is paper-thin with a smooth surface. Zooids are evenly spaced in the firm test in which spicules are crowded throughout, making the surface raspy to the touch. Spicules are to 0.06 mm diameter and are of two types, some (including the larger ones), have sturdy, attenuated, conical rays, 9–11 in optical transverse section and a ray length / spicule diameter ratio up to 0.38. Some of the smaller spicules have up to 13 much shorter rays in optical transverse section, with a ray length / spicule diameter ratio as low as 0.2.

Although the surface is not quilted, deep primary common cloacal canals are the full depth of the zooids. Secondary canals penetrate amongst the thoraces (each with a ventral test strip) isolating them from one another. Zooids have a long thorax, but are not in good condition and the number of stigmata was not determined. The testis is undivided with eight coils of the vas deferens around it. A retractor projects from near the top of the oesophageal neck.

Remarks. The very pointed, slightly attenuated longer spicule rays resemble those of D. roberti , but the presence of a second type of spicule with more and shorter rays and the differences in the form of the colonies distinguish these species from each other.

Figures

FIG. 8. Polysyncraton turris (QM G308538): (A) thorax; (B) abdomen; (C) spicules. Didemnum asterix (WAM 633.88): (D) spicules. Scales: (A, B) 0.1 mm.