Polysyncraton scorteum Kott, 2001

Kott, Patricia, 2007, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 4), Journal of Natural History 41 (17 - 20), pp. 1163-1211 : 1174-1175

Polysyncraton scorteum Kott, 2001

( Figure 7E )

Pyura scorteum Kott 2001, p 135 .

Distribution

Previously recorded (See Kott 2001): South Australia (Great Australian Bight). New records: Tasmanian Canyons (King I. Canyon, 195 m, QM G323343 ) .

Description

A small club-shaped colony to 3 mm diameter has spicules crowded throughout and is raspy on the even, smooth outer surface. Spicules are spherical, to 0.9 mm diameter, with about 15–17 short, rounded to conical rays protruding from the surface. These rays are not crowded together and parts of the globular core of the spicule can be seen between them. Zooids are contracted, appearing as small brown patches crowded in amongst the spicules in this rather crushed and contracted specimen. The atrial aperture is sessile, with a larger anterior lip, the branchial aperture is large and daffodil-shaped and stigmata are in four rows of about seven. A retractor muscle projects from halfway down the oesophageal neck. Gonads were not detected in these zooids.

Remarks

Although gonads were not detected in this specimen, the daffodil-shaped branchial aperture and the long atrial tongue resemble those often found in this genus. Although the spicules are the same size and have numerous short conical rays like those of Didemnum chartaceum , the latter species also has globular spicules with flat-tipped rays that were not detected in the present species. The spicules are identical with those previously described for P. scorteum Kott, 2001 , having rays that vary from rounded to conical. The latter species also has spicules crowded throughout the tough colony and it has a large atrial tongue and branchial siphon like the present species, and it appears to be conspecific with the newly recorded material.

Figures

Figure 7. Scanning electron micrographs. (A) Polysyncraton magnetae (QM G308818); (B) Polysyncraton meandratum (QM G308849); (C) Polysyncraton otuetue (QM G308851); (D) Polysyncraton reticulum (QM G323330); (E) Polysyncraton scorteum (QM G323343); (F) Didemnum abradatum (QM G308870); (G) Didemnum astrum (QM G308857); (H) Didemnum candidum (QM G308765).