Polysyncraton magnetae Hastings, 1931

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 : 741

Polysyncraton magnetae Hastings, 1931

Polysyncraton magnetae Hastings, 1931: 100 ; Kott, 2001: 109 and synonymy.

Distribution. New record: Queensland (Little Broadhurst Reef, QM GH5346). Previously recorded (see Kott, 2001): Queensland (northern and southern Great Barrier Reef).

Description. The newly recorded specimen is a small, hard scrap, probably of a thin sheet-like colony. It is said to have been white in life. Zooids are along each side of deep circular common cloacal canals that surround opaque, slightly elevated stands of spicule-filled test. The branchial apertures are inconspicuous, not being lined with spicules. Spicules are especially crowded in the upper half of the colony and in a layer on the base. Eggs are yellow, but zooids are white in preservative. Spicules to 0.035 mm diameter are a mixture of globular ones with flat-tipped, rodlike rays and stellate ones with sharp conical round-tipped to conical rays, zooids are robust with a thick, short to moderate-length retractor muscle from threequarters of the way down a muscular oesophageal neck. Nine rather fusiform stigmata are in the anterior row. A circle of 10, well-separated, long, clavate testis follicles, each narrowing to a relatively long vas efferens, is surrounded by three loose coils of the vas deferens in the long sac-shaped abdomen.

Remarks. The species has the characteristic common cloacal system (reflected in the quilted appearance of the colony surface caused by depressions over the primary common cloacal canals). Also characteristic are the form and size of the spicules, robust zooids with a muscular oesophageal neck, and the loose cluster ( Kott, 2001: 110, ‘grape-like’) of testis follicles in the long sac-like abdomen. The species has been recorded on only three previous occasions, once from Low Isles and twice from Heron Island. The new record is from the central section of the Great Barrier Reef.