Polysyncraton orbiculum Kott, 1962

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 : 2432-2433

Polysyncraton orbiculum Kott, 1962

( Figure 15B )

Polysyncraton orbiculum Kott 1962, p 300 and synonymy; 2001, p 117.

Distribution

Previously recorded (see Kott 2001): Western Australia (Rottnest I.); South Australia (Gulf St Vincent); Victoria ( Western Port ). New record: SW Australia (Mason Bay, 33 ° 57940S, 120 ° 289100E, WAM 128.90 ) .

Description

The newly recorded colonies are small (less than 1 cm) irregular plates on weed. The characteristic blister-like vesicles surround each stellate branchial aperture on the surface of the colony. Spicules also are characteristic, to 0.05 mm diameter, with 9–11 short, crowded, conical to round-tipped rays in optical transverse section. The zooids are immature.

Remarks

Although these colonies are immature, the circle of vesicles around each branchial aperture and the spicules with their short, crowded rays are characteristic of this temperate species, which so far is known from only relatively few records.

Figures

Figure 15. Scanning electron micrographs of the calcareous spicules of: (A) Polysyncraton millepore (WAM 122.93); (B) Polysyncraton orbiculum (WAM 128.90); (C) Polysyncraton papyrus (SAM E3253); (D) Didemnum astrum (WAM 601.89); (E) Didemnum cilicium sp. nov. (SAM E3251, holotype); (F) Didemnum corium sp. nov. (SAM E3249, holotype); (G) Didemnum cygnuus (QM G308716); (H) Didemnum fragum (SAM E3266).