Eucoelium orientalis (Kott, 1990)

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1622-1623

Eucoelium orientalis (Kott, 1990)

(figure 3A; plate 1B)

Polycitorella orientalis Kott, 1990a: 187 and synonymy.

Distribution. New records: Western Australia (Rottnest I., SAM E2639 E2641; Houtman’s Abrolhos, WAM 768.88). The species was previously known from the Great Barrier Reef (Swain Reefs, QM GH9477: see Kott, 1990a) and Coral Sea.

Description. One colony (SAME2641) is a thick branched stalk, with expanded heads on each terminal branch that fuse with one another; another (SAM E2639) is a single unbranched stalk almost the same diameter as its rounded terminal head; and the third colony (WAM 768.88) is a soft white cushion. Two or three zooids are grouped in conspicuous circular systems and have globular spicules to 0.09 mm diameter with flat-tipped rays. The specimens lack any of the pigment that is characteristic of E. coronaria (see Kott, 1990a, 1992b).

Remarks. Previously (see Kott, 1990a) the species was characterized by its preponderance of globular spicules to 0.035 mm diameter with flat-tipped rays, as well as stellate ones. The newly recorded colonies (from Western Australia) have globular spicules similar to, but larger (to 0.09 mm diameter) than previously reported for this species. Its zooids, as in most specimens of this genus, are in small circular groups of two or three, with the atrial apertures in the centre. Although its range overlaps that of E. coronaria the species are distinct, the present one having spicules of variable size, albeit always predominantly globular, while E. coronaria has stellate spicules to 0.07 mm diameter, with conical rays, conspicuous dark pigment in the colony, and larger circular systems that involve six or more zooids.