Polysyncraton glaucum 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 : 2431

Polysyncraton glaucum Kott, 2001

( Figures 14H , 19A )

Polysyncraton glaucum Kott 2001, p 104 .

Distribution

Previously recorded (see Kott 2001): Queensland (Great Barrier Reef). New record: Northern Territory (Bynoe Harbour, QM G308736 ) .

Description

The newly recorded colony is a thin encrusting sheet with spicules crowded in the surface, and present, although not crowded, through the remainder of the colony. Spicule-filled papillae are on the ventral side of each branchial aperture. The extensive common cloacal cavity is at thorax level. Although the preserved specimen is mutilated and squashed, the form of the systems is evident in the in situ photograph showing white-rimmed common cloacal apertures evenly distributed over the surface of the colony in the centre of green areas dotted with white, spicule-filled branchial apertures. White spicule-filled ridges surround these green circular to polygonal areas that each represent a single common cloacal system.

Remarks

Photographs of the newly recorded specimen show it to be identical with the type material ( Kott 2001, Plate 5E). The species appears to be related to the group of Polysyncraton spp. which has independent common cloacal systems (see P. galaxum , Remarks, above). The green colour of the present species and its flat systems level with the upper surface help to distinguish it from the red-pink P. galaxum in which each system is contained in a lobe projecting from the upper surface of the colony. Polysyncraton pavimentum Monniot, 1993 and Polysyncraton polysystema sp. nov. (. P. pavimentum: Kott, 2002a ), also have flat common cloacal systems but they are pale pink. The latter species also has the same spicule diameter (0.08 mm) and number of rays in optical transverse section (9–11) as the present species. However, its spicule rays are conical with pointed or truncated tips rather than being long and blunt-tipped as they are in the present species.

Figures

Figure 14. Scanning electron micrographs of the calcareous spicules of: (A) Leptoclinides decoratus (SAM E3257); (B) Leptoclinides dubius (WAM 1093.89); (C) Leptoclinides frustus sp. nov. (SAM E3255, holotype); (D) Leptoclinides kingi (WAM Z20557); (E) Leptoclinides minimus sp. nov. (WAM 30.84, holotype); (F) Leptoclinides pulvinus sp. nov. (QM G308742, holotype); (G) Polysyncraton galaxum (SAM E3250); (H) Polysyncraton glaucum (QM G308736).

Figure 19. In situ images of: (A) Polysyncraton glaucum (QM G308736); (B) Polysyncraton papyrus (SAM E3253); (C) Polysyncraton pedunculatum (SAM E3272); (D) Polysyncraton purou (QM G308707); (E) Polysyncraton rica (SAM E3245); (F) Didemnum cilicium (SAM E3251, holotype); (G) Didemnum corium (SAM E3249, holotype); (H) Didemnum cygnuus (QM G308716).