Culeolus anonymus Monniot and Monniot, 1976

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 : 344-346

Culeolus anonymus Monniot and Monniot, 1976

(®gure 25)

Culeolus anonymu s Monniot and Monniot, 1976: 645; 1982: 121 (part, probably not Plate 3D); 1985b: 31; Sanamyan and Sanamyan, 1999: 1862.

Culeolus suhmi: Millar, 1959: 199 (part, only specimens with incomplete ring of papillae from st. 663 and 668); 1970: 136.

Material examined. St. 896, 5651±5530 m, one damage d specimen; st. 4086, 6130± 6420 m, one damage d specimen; st. 4089, 5063±5470 m, one specimen; st. 4090, 6145± 5680 m, two specimens; st. 4102, 5145±5150 m, one specimen attached to empty test of Situla ; st. 4104, 5110±5120 m, three specimens, two of which badly damaged; st. 4109, 5225 m, two specimens.

Description. The body shape and structure of the test surface is similar to C. antarcticus , but the postero-ventral crest is diOEerent, it lacks a mid-ventral branch and has an arc of papillae only around the posterior end of the body, which is opened dorsally (®gure 25A). Internal features conform to previous descriptions, but length and position of the gonads are more variable than was formerly thought. Each gonad consists of two to four, rarely up to seven lobes. The anterior gonad is usually longer than the posterior. In typical specimens (®gure 25B) the right gonads are nearly parallel to the endostyle, and at least the distal part of the anterior gonad overlaps the posterior gonad, and gonads terminate not far from each other. On the left, the proximal half of the anterior gonad usually extends posteriorly from the pole of the gut loop to about halfway down the descending limb and ends far from the anus. In the specimen from st. 4109, however, the anterior gonad on the left side is longer, extending along the whole descending limb of the intestine to open near the anus. In other specimens, anterior gonads on both sides are further forward, the left one at the level of the pole of the gut loop (specimen from st. 4089), or even slightly anterior to it (st. 4086). The anal border has two large lobes, but it was not possible to determine if they are subdivided or smooth.

Remarks. All the present specimens, recorded not far from the type locality, conform well to the original description apart from the above-mentione d variations in position of the gonads in some specimens, and we have no doubt that they are conspeci®c with material described by Monniot and Monniot (1976). The validity of the species is, however, not so obvious. Monniot and Monniot (1976) give only general remarks on the genus Culeolus and provide no direct comparison of their species with other related Atlantic species, in particular with C. suhmi Herdman. According to their table 2 (Monniot and Monniot, 1976: 648), C. anonymus diOEers from C. suhmi in the structure of the anus and in relative position of gonads to each other and to the gut loop. Indeed, in specimens described as C. suhmi by Monniot and Monniot (1973), the gonads look diOEerent from those of C. anonymus , being well separated from each other on the right side, and on the left the anterior gonad is close to the pole of the gut loop. But in another specimen of C. suhmi ( Monniot and Monniot, 1985a, ®gure 10a) and also in specimens from the central Atlantic described below, the gonads appear exactly as in C. anonymus . The structure of the anus cannot be used to separate these species, originally it was described as smooth, but later as having`four or ®ve lobes more or less divided’ ( Monniot and Monniot, 1982: 122). The two species, however, have diOEerent postero-dorsal crests, which completely encircle the posterior end of the body in C. suhmi , but are open dorsally in C. anonymus .

In all our specimens of C. anonymus from the south-west Atlantic and also from the south-west Paci®c (see Sanamyan and Sanamyan, 1999), the postero-dorsal crest consists of papillae. Although two populations of this species were described originally, one with the crest consisting of separate papillae, and the other with a continuous crest, many intermediate specimens were found subsequently. A similar range of variation in the structure of the crest was found in C. antarcticus and this feature may be considered as intraspeci®c variation. However, the general shape of the crest, as it is in C. antarcticus , seems to be a much more stable character in the present, and probably in other species of Culeolus . It is the single character distinguishing C. anonymus from C. suhmi , but its validity needs to be con®rmed in additional material from the north and central Atlantic (where only C. suhmi is known).

Millar (1959) doubted that the specimens from the Kermadec Trench Sts 663 and 668 (but not DF661: Monniot and Monniot, 1982, sic) belonged to C. suhmi , as they had an interrupted dorsal crest. They are synonyms of C. anonymus as it is presently de®ned. Specimens ®gured on Plate 3D by Monniot and Monniot (1982) probably belong to another species, as they appear to have a complete ring of papillae.

Monniot and Monniot (1982: 121) revised the holotype of C. wyvillethomsoni Herdman, 1881 and found it very similar to an abnormal specimen of C. anonymus , with only one left gonad, described by Monniot and Monniot (1976). They wrote:`The lack of one gonad may or may not be an anomaly, but we do not fully believe in two species. Nevertheless, we prefer to maintain Herdman’s species with a single individual to avoid having an important anatomical diOEerence between a species and its holotype.’ Although the latter statement is not a valid reason to cast aside the prior name, we prefer to use C. anonymus as a valid name, because we are not completely sure it is a junior synonym of C. wyvillethomsoni Ðall the present specimens have two gonads on each side and, although the number of gonads varies in some species of Culeolus (e.g. C. suhmi: Millar, 1955 ), it may be stable in others (e.g. C. antarcticus ).