Aplidium hyacinthum, Kott, 2008

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 : 1156-1158

Aplidium hyacinthum sp. nov.

( Figures 9A–C )

Distribution

Type locality: Western Australia CSIRO SS10 / 05 (Albany, Stn 22, 118.2940E 35.3350S, 100 m, 22 November 2005, holotype WAM Z27516 , QM G328108 ; paratype QM G328109 ) .

Description

Holotype and paratype each consist of two opaque, orange-coloured, long, firm cylindrical stalks (15× 16 mm and 10× 8 mm respectively) joined basally. Sparse but evenly distributed sand is embedded in the translucent internal test as well as in the opaque external layer of the stalk. A translucent terminal cap-like head, sometimes pointed and sometimes rounded, is on the top of each stalk. Short rows of zooids in the head converge to a large terminal common cloacal aperture. The branchial and atrial apertures are relatively close to one another, the branchial aperture on a short six-lobed siphon and the atrial aperture has a large and often bifid or trifid tongue from the anterior rim of the opening. Twelve rows of stigmata, each half-row with about 25 stigmata, are in the branchial sac. The stomach, halfway down the abdomen, has 30 fine parallel folds in its wall. The posterior abdomen is very long, extending down into the base of the stalk.

Remarks

The appearance of this species with its long orange stalks is unusual. Other known species with relatively narrow, long but not such regularly cylindrical stalks and an atrial tongue from the upper rim of the opening are A. australiensis Kott, 1963 (with a thin leathery stalk, large head and only 16 folds of the stomach wall); A. bacculum Kott, 1992a with branched and irregular stalks, only five rows of stigmata and five deep stomach folds; A. brevilarvacium Kott, 1963 with similar cap-like heads on narrow but branched stalks and zooids with 10 stomach folds; and A. geminatum Kott, 1992a with a thick transversely wrinkled stalk and a number of cloacal systems in each large almost spherical head. One of the few species with a similar number of longitudinal folds in the stomach wall and a similarly large, wide pharynx, A. uteute Monniot and Monniot, 1987 , forms flat-topped cushions and sheets or vertical mushroom-like colonies always with a number of simple circular systems of zooids in each colony contrasting with the

colonies of the present species with their cylindrical stalks each supporting a single cloacal system with a terminal common cloacal aperture.

Figures

Figure 9. Aplidium hyacinthum sp. nov. (QM G328108): A, colony; B, thorax and abdomen; C, part of posterior abdomen. - Aplidium magnilarvum (D, G, QM G328442; E, F, QM G328101): D, colony; E, thorax and abdomen; F, anterior part of posterior abdomen showing large egg; G, larva Scales: A, D, 1.0 cm; B, C, E, F, 0.5 mm.