Polysyncraton linere, 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 : 738-739

Polysyncraton linere sp. nov.

( figure 4 )

Distribution. Type locality: Victoria (Western Port, 23 m, 25 November 1974, holotype MV F70228 ).

Description. The thin encrusting colony has spicules crowded in the surface test and in the floor of the horizontal thoracic common cloacal cavity, but are not present in the translucent basal test beneath the common cloacal cavity. Spicules are to 0.07 mm diameter and have 9–11 short rounded projections (rather than conical rays) in optical transverse section. These projections are not crowded, and are evenly spaced on a large spherical central mass.

Zooids have a short branchial siphon with six pointed lobes around the aperture. The rim of the atrial aperture flares out, but lacks an atrial lip. Eight stigmata are in the anterior row of the branchial sac. Five coils of the vas deferens surround about five male follicles. A retractor muscle was not detected. The larval trunk, 0.5 mm long, has the tail wound three-quarters of the way around it and six pairs of lateral ampullae. Blastozooids were not detected.

Remarks. Polysyncraton victoriensis Kott, 1976 and Didemnum turritum: Kott, 1976 , known only from Western Port, are distinguished from the present species by their deep primary common cloacal canals, forked atrial tongue, smaller spicules to 0.04 mm diameter ( Kott, 1976: 0.4 m sic) with about seven conical pointed rays in optical transverse section crowded throughout. Polysyncraton lithostrotum ( Brewin, 1956) from New Zealand has similar spicules, but its isolated common cloacal systems distinguish it.

Figures

FIG. 4. Polysyncraton linere (MV F70228): (A) thorax; (B) abdomen; (C) larva; (D) spicules. Scales: (A–C) 0.1 mm.