Polysyncraton rica Kott, 2001

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 : 745

Polysyncraton rica Kott, 2001

( figure 7 B–D)

Polysyncraton rica Kott, 2001: 130 .

Polysyncraton aspiculatum: Kott, 1997: 1176 .

Polysyncraton pedunculatum: Kott, 2001: 121 (part, QM GH2387).

Distribution. New records: South Australia (Top Gallant I., QM GH967; Pearson I., QM GH966; Investigator Group, QMG2387). Previously recorded (see Kott, 2001): South Australia (Kangaroo I.).

Description. Known colonies are irregular cushions divided into several rounded lobes about 2 cm in diameter. A surface bladder-cell layer is conspicuous over a crowded layer of spicules. Spicules are also present but sparse and patchy in the basal test (beneath the zooids). They are stellate with robust, sometimes sharply angled, almost pyramidal rays, often broken at their base, and sometimes with bifid tips. As previously described they sometimes are bilaterally rather than radially symmetrical and have 11–13 rays in optical transverse section. The primary common cloacal canals surround large groups of zooids and are continuous with posterior abdominal spaces traversed by a test connective between basal test and each zooid clump. Common cloacal cavities penetrate into the clump around the thoraces. Two or three large, sessile, but not necessarily terminal common cloacal apertures with spicule-filled projections of the test around their rims, are randomly placed on each lobe. Colonies are said to be blue / green in life, although one contracted colony (QM GH5426: Kott, 2001: pl. 6G) is bluish red beneath the translucent superficial layer of bladder cells. Colonies are orange in short-term preservative, the preservative also becoming orange. In long-term preservation the colonies become cream.

Zooids are relatively small, but those in the vicinity of the common cloacal apertures have particularly long and often wide atrial tongues. A very fine retractor muscle projects from the top of the oesophageal neck. A small circular lateral organ is on each side of the endostyle at about mid-thorax level. The post-pyloric part of the gut loop is flexed ventrally with gonads against the dorsal side of the flexure. Seven or eight testis follicles are surrounded by three coils of the vas deferens.

Larvae are present in the soft central test of colonies collected in March (QM GH966–7) and April (QM GH2387). The trunk is 0.8 mm long and the tail is wound two-thirds of the way around it. Eight long lateral ampullae are each side of the three antero-median adhesive organs and a long external horizontal ampulla is on the left projecting back between the oozooid and a thoracic blastozooid, each with four rows of stigmata. A constricted waist is around the larval trunk behind the lateral ampullae.

Remarks. The preserved colonies resemble the sympatric, aspiculate Polysyncraton pedunculatum in general appearance, although they lack the stalk of the latter species (see also P. pedunculatum , ‘Remarks’ above).

Figures

FIG. 7. Polysyncraton pedunculatum (QM GH962): (A) larva. Polysyncraton rica (QM GH966): (B) colony; (C) larva; (D) spicules. Scales: (A, C) 0.1 mm; (B) 1.0 mm.