Aplidium clivosum Kott, 1992

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1150-1151

Aplidium clivosum Kott, 1992

( Figure 7D )

Aplidium clivosum Kott, 1992a, p. 530 and synonymy; Kott 2004b, p. 48.

Distribution

Previously recorded (see Kott 2004b): Western Australia ( Ashmore Reef, Port Hedland, Montebello I., Cockburn Sound, Geographe Bay, Hamelin Bay); South Australia (Great Australian Bight, Spencer Gulf, Gulf St Vincent, Kangaroo I., Flinders I.); New South Wales (Jervis Bay); Queensland (Heron I.). New records: Western Australia CSIRO SS10/05 (Bald I., Stn 38, 169 m, 24.11.05, QM G328127; Pt. Hillier, Stn 57, 195 m, 27.11.05, QM G328099; Jurien Bay, Stn 83, 113 m, 02.12.05, QM G328160).

The species is known from around the Australian continent in temperate to tropical waters but has not yet been recorded outside these waters.

Description

Newly recorded colonies are mushroom-like, with a flat upper surface or sometimes an almost spherical head and a sandy stalk which branches into prop-like structures basally. Sometimes the sandy sides of the colony tend to overlap the upper surface. Two to four shallow, wide depressions up to 2 cm in maximum extent are in the upper surface. The surface test may slightly overlap the margins of these wide depressions. Double rows of zooids line the canals that converge to the large common cloacal apertures on conical protrusions more or less in the centre of each of these depressions. Sand is crowded on the upper surface and around the sides of the colony and forms a thin, hard crust that usually obscures the position of the zooids. Sand is less crowded internally. The test is transparent but firm. It has minute purple cells scattered through it. Zooids are a dark reddish-purple and criss-cross through the internal test of the colony. They are as previously described (see Kott 1992a) with a long branchial siphon, six well-formed lobes around the branchial aperture and a short, conspicuous branchial sphincter. A large atrial tongue projects from the body wall just anterior to a short siphon. Up to 20 rows of about 12 stigmata are on each side of the thorax. The stomach is halfway down the abdomen and has five conspicuous folds in its wall. The long hair-like posterior abdomen contains double rows of male follicles. In these specimens it is contracted and the vas deferens convoluted.

Remarks

These robust colonies are characterized by the large depressions in the upper surface in which double rows of zooids converge to a limited number of conical protrusions with terminal common cloacal apertures. The colonies and zooids have a superficial resemblance to those of A. crateriferum , although the latter species has smaller cloacal cavities surrounded by zooids rather than the long converging double rows of zooids in the present species. Both Aplidium grisiatum Kott, 1998 (which has zooids with eight or nine stomach folds rather than the five in the present species) and Synoicum castellatum Kott, 1992a (with zooids with the characters of Synoicum rather than the folded stomachs of Aplidium spp ) have colonies that superficially resemble the present species.

Figures

Figure 7. Synoicum sphinctorum (QM G328068): A, larva. Synoicum vesica sp. nov. (QM G328100): B, colony; C, zooid. Aplidium clivosum (QM G328133): D, colony. Aplidium crateriferum (E1–2 QM G328113; F, G, QM G328111): E1–2, colonies; F, thorax and abdomen; G, posterior abdomen showing male follicles. Scales: A, C, F, G, 0.2mm; B, D, E, 1.0 cm.