Corynascidia suhmi Herdman, 1882

Sanamyan, K. E. & Sanamyan, N. P., 2002, Deep-water ascidians from the south-western Atlantic (RV Dmitry Mendeleev, cruise 43 and Academic Kurchatov, cruise 11), Journal of Natural History 36 (3), pp. 305-359 : 335-337

Corynascidia suhmi Herdman, 1882

(®gure 19) Corynascidia suhmi Herdman, 1882: 186 ; Kott, 1969: 87; Millar, 1988: 1429; Monniot and Monniot, 1994: 22.

Material examined. St. 4090, 6145±5680 m, two specimens.

Description. The specimens are about 10 cm long. The test is thin, transparent and so soft, that it is di cult to recognize its real shape and dimensions. The anterior end of these long specimens is about 2 cm wide and the body gradually tapers to the peduncle. The test on the peduncle is a little thicker and more rigid. The peduncle is about half the body length and contains an extension of the body wall. Its posterior end is ¯attened and does not have any root-like outgrowths, suggesting that the specimens were attached to hard substratum. Large, obscurely lobed apertures are on the side of the body. The branchial aperture is in the middle of the lower half of the body, the atrial is halfway between the branchial aperture and the top.

The circular siphonal muscles are thin. About eight short, thick parallel longitudinal muscles extending from each side of the dorsal mid-line between the siphons are in a continuous series with the radial muscles from each side of the base of the siphons. They all terminate abruptly in a vertical line not more than halfway down each side of the body. Bundles of muscle bands above the anal siphon and below the branchial siphon cross the mid-dorsal line. Other longitudinal muscles do not cross the mid-dorsal line (®gure 19A).

At least 150 long tentacles of several orders arise from a low muscular velum. The prepharyngea l groove lacks a dorsal V and has two well-separated rims. A large elongate neural gland is on one line, anterior to the ganglion, and has a large anterior opening. The dorsal lamina has one line of long languets. The branchial sac projects into the anterior part of the peduncle. The thick long endostyle extends from the branchial opening, curves on the top of the peduncle, and turns up along the ventral side of the body. It was not possible to distinguish between the endostyle and the retropharyngea l groove. The branchial tissue is delicate. Transverse rows of spiral stigmata extend along the long axis of the body. Each side of the branchial sac has about 60 rows of about 50 spirals with 1.5±2.5 coils. Spirals are not very regular, between large spirals small additional (interstitial) ones are occasionally present. Rows are separated by ¯at transverse vessels. Long branchial papillae arise from the transverse vessels, and, occasionally, from spirals or even from radial vessels. Many papillae are T-shaped, but in some places longitudinal vessels persist. There are about two longitudinal vessels per spiral (®gure 19C).

The gut lies along the mid-line of the body and is not displaced to either side. A short straight oesophagus opens close to the upper extremity of the body. In both specimens the globular stomach is distinctly demarcated from the oesophagus and from the intestine. In one specimen it has rather distinct internal longitudinal folds, which have disintegrated in the other specimen. The intestine curves immediately behind the stomach, runs beside the stomach and oesophagus, and then curves across the oesophagus and runs up to the atrial opening as a long, straight rectum which terminates in an anus fringed with long ®nger-shaped lobes below the atrial ori®ce.

Gonads are well developed. The elongate ovary is between the intestine and the stomach and testis follicles are spread around the ovary and between the stomach and the body wall. Gonoducts run along the rectum and end above it, their openings were not seen.

Remarks. This is the type species of the genus. It has been seldom recorded and only few specimens are known. We cannot agree with the existing opinion ( Millar, 1988), that C. herdmani may be conspeci®c with this species. They diOEer in many characters, including position of the siphons and especially in the shape and orientation of the gut loop.

Although the gut loop is median in this species, its course is characteristic of the Corellidae with the intestine (or distal limb of the loop) posterior to the oesophagus and stomach (constituting the proximal limb) and the rectum crossing over the oesophagus before running anteriorly to the atrial aperture.