Cnemidocarpa bythia ( Herdman, 1881 )

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 : 340-341

Cnemidocarpa bythia ( Herdman, 1881)

(®gure 22) Cnemidocarpa bythia: Millar, 1959: 194 ; Monniot and Monniot, 1973: 432; 1974: 752; 1977b: 313; 1982: 113; 1985b: 27; Monniot, 1998: 552.

Material examined. St. 4104, 5110±5120 m, four specimens, two of which are badly damaged.

Description. The specimens are attached to small stones. They are small, sessile, hemispherical or upright and cylindrical, the larger is 4 mm high and 3.5 mm wide. The sessile apertures are on the upper surface. The tunic is thick but not hard. Its super®cial layer is covered by numerous, minute, crowded spherules, resembling those of Styela coriacea (Alder and Hancock) , and it has a velvet-like appearance. The tunic has neither root-like outgrowths nor foreign particles attached to it.

The body wall is thick and muscular. About 12 large and a number of smaller branchial tentacles arise from the rim of a high velum. There is an atrial velum covered by thin atrial tentacles. Similar tentacles are present on the test lining the branchial siphon. The prepharyngeal band is composed of a single high undulating lamella, there is an inconspicuous dorsal V around a small dorsal tubercle. The neural ganglion is just posterior to the dorsal tubercle and situated half way between the siphons. A high and folded dorsal lamina has numerous long languets on its rim. The branchial sac is dense and has four prominent folds which have no clear limits, the larger folds have about 14 internal longitudinal vessels, and three or four vessels are between the folds. A few transverse stigmata are present on the bottom of the branchial sac of one specimen, but we did not ®nd them in another dissected specimen .

One elongate gonad of the Cnemidocarpa - type is present on each side of the body. Large male follicles are along the whole length of gonad, between the gonad and the body wall. The gonads are loosely attached to the body wall close to the mid-ventral line, and the ducts, directed to the atrial ori®ce, open far from it.

The small stomach has seven or eight wide longitudinal folds and a conspicuous caecum. The anal border is distinctly lobed. Two or three large and several small endocarps are present on each side of the body. The structure of the inner surface of the body wall of both dissected specimens is identical and peculiar. It is completely covered with crowded, low and nearly rectangular elevations, looking like numerous papillae.

Remarks. The species can be easily distinguished by the presence of minute spherules in the tunic and by the dorsal lamina with languets. Transverse stigmata on the bottom of the branchial sac are known for several Styelidae , but they were not previously reported for this species. The present specimens have a lobed anus, as in the specimens described by Monniot and Monniot (1973) from the north Atlantic, while the specimens from the Tasman Sea and the Kermadec Trench, described by Millar (1959), have a smooth anus. The presence of transverse stigmata (protostigmata) and a lobed anus may constitute valid characters for separation of an Atlantic from a Tasman Sea species. The species has been recorded from the Atlantic, Indian and Paci®c oceans and around the Antarctic, but although records are numerous, most of them lack descriptions, and additional material is required to con®rm possible diOEerences between Atlantic and Paci®c specimens.

Cnemidocarpa drygalskii ( Hartmeyer, 1911) Tethyum drygalskii Hartmeyer, 1911: 452 .

Cnemidocarpa drygalskii: Monniot and Monniot, 1983: 69 (synonymy); Sanamyan and Sanamyan, 1999: 1850.

Material examined. St. 4100, 1265± 1376 m, two specimens. Remarks. Two small hemispherical juvenile specimens attached to the test of Corella eumyota appear to be of this species. However, the gonads are not developed and therefore the identi®cation is tentative.