Polysyncraton papyrus Kott, 2001

Kott, Patricia, 2005, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3), Journal of Natural History 39 (26), pp. 2409-2479 : 2433

Polysyncraton papyrus Kott, 2001

(Figures 5A–C, 15C, 19B)

Polysyncraton paradoxum: Kott 1954, p 163 .

Polysyncraton papyrus Kott 2001, p 120 .

Distribution

Previously recorded (see Kott 2001): Tasmania (NE coast). New record: South Australia (Kangaroo I., SAM E3253 ) .

Description

The newly recorded specimen consists of fragments of a soft, thin sheet. The surface appears spotted to the naked eye owing to the daisy-like patterns created by the spicules crowded into each of the six lobes of the branchial apertures that project slightly from the upper surface. Spicules are evenly, but rather sparsely distributed in the remainder of the surface test and on the base of the colony. They are not present in other parts of the colony. Spicules are small, to 0.035 mm diameter, and they have 9–11 short conical rays in optical transverse section. In preservative, the pinkish brown zooids can be seen through the surface but in life the colony is a translucent greyish blue colour. Common cloacal apertures protrude from the surface. About seven spicule-filled radial ribs extend from the aperture across the roof of the common cloacal cavity. The thin test over these common cloacal cavities may be elevated in life when the internal pressure is maintained by the ciliary current. The thoracic common cloacal cavity surrounds clumps of thoraces and the abdomina are embedded in the basal test.

Thoraces are relatively large with about 10 narrow, spindle-shaped stigmata per row. Branchial lobes are narrow and pointed. The atrial aperture completely exposes the branchial sac to the common cloacal cavity and an anterior atrial lip is short and bifid. The vas deferens coils five times around four or five testis follicles. A retractor muscle was not detected.

Remarks

The type specimens of P. papyrus have similar spicules but they are more crowded than they are in the newly recorded specimen and the zooids have a retractor muscle. Other characters appear to be similar and confirm Kott’s (1954) description of the types and in particular the gonads, with five coils of the vas deferens (see Kott 2001).

The spindle-shaped stigmata have been reported for Leptoclinides brandi and the spicule-filled branchial lobes forming petal-like patterns on the surface have previously been reported for Didemnum cygnuus Kott, 2001 and some specimens of Polysyncraton cuculliferum . Neither of these characters appears to have any phylogenetic significance.