Kaikoja multitentaculat

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 : 320-321

Kaikoja multitentaculat a ( Vinogradova, 1975)

(®gure 10)

Situla multitentaculata Vinogradova, 1975: 290 .

Material examined. St. 4103, 4485±4520 m, one specimen.

Description. The single specimen is in poor condition and it is not possible to provide a complete description. There is a distinct hollow cylindrical peduncle about 2±3 cm wide and 12 cm long with a tuft of hair-like processes on the area of attachment. The shape of the body is obscured, the thin soft test being cut in many places. It is about 20 Ö 15 cm when expanded. The body is a thin ¯at disk, badly damaged and no longer attached to the test. Continuous circular muscle bands are around the periphery of this disk, radial muscles are absent. Circular muscles extend somewhat beyond the line of the tentacles, but do not reach the prepharyngeal groove. Tentacles on a low but distinct velum are elongate, leaf-like, numerous and crowded. Some of them have a hemispherical ampulla near the base (®gure 10A). Dorsally, the prepharyngeal band is far from the branchial sac and from the row of tentacles, and has a long narrow indentation. The entire surface between the tentacles and the branchial sac is covered by sensory papillae. Lateral and ventral parts of the disk are damaged and their structure obscured. The branchial sac is in shreds. Its entire surface is covered by two kinds of papillae: evenly distributed, short, ¯attened papillae, and long narrow papillae con®ned mainly to large vessels (®gure 10B). The latter resemble the branchial papillae of some Agneziidae . The shape of the perforations and the net of thick and thin anastomosing branchial vessels appears to resemble closely that of Benthascidia michaelseni Ritter, 1907 , as shown in the photograph reproduced by Monniot (1998, ®gure 3E) (but B. michaelseni lacks branchial papillae). The oesophageal opening is surrounded dorsally and on the left side by a dense tuft of long, crowded papillae.

Remarks. The species was previously known only from a single specimen from the South Sandwich Trench. Monniot (1998) designated it as a type species of Kaikoja Monniot, 1998 , distinguished from Situla by`disappearance of the radial musculature, reducing the ability to close the mouth on prey, and the disappearance of the dorsal lamina’ and from Benthascidia by the presence of long branchial papillae ( Monniot, 1998: 551). However, Situla pelliculosa Vinogradova, 1969 , the type species of Situla , does not have the ability to close its mouth on prey, and has weakly developed radial musculature, and thus these features cannot be used for separating Kaikoja from Situla . Monniot (1998: 550) supported the hypothesis that the cluster of papillae at the oesophagus entrance is a condensed dorsal lamina because`no branchial diOEerentiation exists dorsally close to the oesophagus’. However, the dorsal lamina was ®gured and described in the detailed original description of S. multitentaculat a as a low continuous band, running from the dorsal margin of the perforated zone of the branchial sac to the oesophagus opening. In the present specimen this region of the branchial sac is damaged and cannot be examined. In our opinion, it is unlikely that these papillae are remains of the dorsal lamina. Thus, the only signi®cant feature separating Kaikoja from Situla is the presence of branchial papillae in Kaikoja .

The related genus Benthascidia , based on two specimens, which were recently redescribed by Monniot (1998), is probabl y intermediate between Kaikoja and Situla , or it may be congeneric with Situla . The structure of this genus is too poorly known to determine its exact taxonomic relationships.