Perophora longicaulis, KOTT, 2003

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1633-1634

Perophora longicaulis , sp. nov.

(figure 4A–D)

Distribution. Type locality: Western Australia (Houtman’s Abrolhos, Wallabi Group, SW Long I., slope of lagoon, 18 m, coll. L. Marsh, 25 March 1987, holotype WAM 206.87. There are no other records.

Description. The colony has a basal network of branching and anastomosing vessels forming a thin membrane where they join. Vertical stalks, each with a terminal zooid, project from the basal network. Each stalk is from twice to four or five times the zooid length (to 3 mm). The test is delicate and transparent with an inconspicuous vascular network. Three vessels extend down into the stalk from the ventral sinus, the central one sometimes is thicker and expands into a vascular network in the top of the stalk.

The branchial and atrial siphons are small. The branchial aperture has seven rounded lobes and the atrial aperture six. The atrial aperture tends to be terminal and the branchial aperture is orientated obliquely antero-laterally. Body muscles are numerous and fine, extending from the branchial and atrial siphons, the ventral ones terminating on each side of the endostyle and the dorsal ones fading out before reaching the posterior end of the body.

Four rows of about 30 long narrow stigmata are in the branchial sac. Longitudinal vessels are all interrupted, being represented by about 10 papillae with long biramous arms, one arm extending anteriorly and the other posteriorly. Curved dorsal languets are on the transverse vessels where they cross the dorsal lamina. The proximal limb of the gut loop is partly behind the branchial sac, rather than being entirely in the parietal body wall to the left of the pharynx, although the distal limb of the relatively narrow loop is on the left. The retropharyngeal groove therefore passes alongside the large spherical stomach about half-way down its right side, and along the duodenum and long posterior stomach. The gut expands abruptly into the rectum just distal to the pole of the loop and extends dorsally, bending anteriorly at the dorsal border of the pharynx. Gonads, in the gut loop, consist of about 10 pyriform testis follicles in an arc around the inside of the pole of the loop. Their ducts join the vas deferens which crosses the sac-like ovary and extends up to open, with the anus, near the atrial aperture.

Remarks. Like Perophora modificata Kott, 1985 the species has only four rows of stigmata and a vascular projection from the ventral sinus in the top of the stalk. It is distinguished by its shorter testis follicles, very much longer zooid stalks, fewer stigmata and the absence of entire longitudinal vessels.

The species that resembles the present one most closely is Perophora japonica Oka, 1927a , from Honshu, Japan which has similar gut loop, gonads and apertures, four rows of stigmata and biramous branchial papillae (rather than entire longitudinal vessels). The Japanese species has recently been found to have been introduced to European waters (Nishikawa et al., 2000). It has fewer and more-lobed testis follicles, shorter and fewer muscles and it lacks the long zooid stalks and the posterior vascular projection of the present species, which appears to be indigenous.