Aplidium laticum, Kott, 2006

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 207

Aplidium laticum sp. nov.

( Figure 6F, G )

Distribution

Type locality. Tasmanian Canyons (38.11482 ° S, 149.3565 ° E, Banks Strait, 168 m, 25 April 2004, Sherman sled, species 10, syntypes two QM G308832 ; King I. Canyon, 294 m; Pieman Canyon, 176 m; Big Horseshoe, 159 m) .

Description

Colonies are sessile globes or cones or stumpy upright lobes, fixed to the substratum by a sandy hold-fast in the centre of the lower surface. The test in all the recorded specimens is soft and almost liquid and the arrangement of the zooids was not determined.

In most of the specimens, the zooids are in vegetative phase, with small, juvenile regenerating thorax and abdomen on a long posterior abdomina. Details of the zooid structure could be determined in only a few zooids in the syntype colonies. The zooids are long and thin as in many species in this genus. The atrial tongue arises from the anterior rim of the aperture and the thorax is long and narrow with 18 rows of about 20 stigmata. The abdomen is relatively short with five gastric folds and the posterior abdomen is long and narrow.

Remarks

The almost liquid test of this species is reminiscent of the test of Pseudodistoma fragilis Tokioka, 1958 (from Japan) and P. gracile Kott, 1992a from the tropical Western Pacific (see Kott 1992a). However, the zooids in the syntype material are characteristic of the genus Aplidium . Although known species often have zooids and even colonies that generally resemble those of the present species, an Aplidium species with its very soft test has not been encountered and the species is not readily assigned to any known Australasian or sub-Antarctic species.

Figures

Figure 6. (A–E) Aplidium formosum (holotype SAM E2899): (A) colony; (B) thorax, abdomen, and proximal part of posterior abdomen, showing ovary; (C) posterior abdomen showing male follicles; (D, E) larvae. (F, G) Aplidium laticum (syntype QM G308832): (F) thorax and abdomen; (G) posterior abdomen. Scale bars: 1 cm (A); 0.2 mm (B, C, F, G); 0.1 mm (D, E).