Brevicollus tuberatus Kott, 1990

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1625

Brevicollus tuberatus Kott, 1990

(figure 3B–D)

Brevicollus tuberatus Kott, 1990a: 237 .

Distribution. New records: New South Wales (inside Lighthouse Reef, Ulladulla, QM G308571). The species previously was known only from the type and paratype, from South Australia and Gabo I. (eastern Victoria) from 10 to 15 m depth. The new record is from 1 to 4 m.

Description. The colony is firm and irregular growing around weed stalks. Sand is embedded throughout. Numerous longitudinal muscle bands on the thorax remain separate and do not form a continuous coat. Only a few transverse muscles are beneath the longitudinal ones, which continue in a wide band along each side of the abdomen. In adult zooids five rows of about 35 stigmata per row are present, each crossed by a parastigmatic vessel. Juvenile vegetative zooids have 18–20 stigmata per row. The gut loop is short, the abdomen about the same length as the thorax. The stomach is a relatively small barrel with 12 shallow parallel longitudinal folds about half-way down the gut loop. Gonads are in the loop at the posterior end of the abdomen. The posterior abdominal vascular process is variable in length, but always fine. About five larvae are in the posterior half of the right side of the atrial cavity in these zooids. They have a relatively short but deep trunk as previously described (Kott, 1990a) with two rows of stigmata in the larval pharynx, a long, vertical gut loop, a large yolk mass and the adhesive organs sessile and depressed into the trunk.

Remarks. Although a few more stomach folds were counted than in the types, the newly recorded specimen resembles the type material in most significant respects. The presence of parastigmatic vessels and the relatively large zooids are all unusual features of this species, and the larvae are unique. The phylogenetic relationships of this genus are obscure and its assignation to the Polycitoridae is based solely on the separately opening six-lobed apertures and the location of gonads in the gut loop (although the abdomen is relatively short). Parastigmatic vessels do occasionally occur in Holozoidae , but the genus does not have any other affinities with that family (in which there is a pronounced vegetative stolon).