Culeolus uschakovi, Redikorzev, 1941

Culeolus uschakovi View in CoL ,

presently deposited in the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia, and labelled l Zool. Mus. Acad. Sci. No. 53-1934/1771 , bore the following information: Culeolus uschakovi Redik. /Typ./St. 208, 2. VII. 1932, Sea of Okhotsk ; 46°41′5N, 147°28′0E, Dredge, 3350 m deep, silt and pebbles, R(esearch)/ t(rawl) l Gagara z, P. Ushakov. z (original in Russian). This was entirely consistent with the sampling information originally provided by Redikorzev (1941); Sea of Okhotsk : St. 208, depth 3350 m, silt, pebble, 1 specimen. (P. Ushakov) (p. 183, in Russian) and l Ochotsk-Meer: 46°41′5N, 147°28′E, 3500 m Tiefe , Schlamm , Geröll (1 EX.) z (p. 211, in German summary). The identity of the specimen as the holotype (by monotypy) of Culeolus uschakovi was unquestioned. The body proper of the specimen had been cut open longitudinally from the branchial to atrial apertures along the dorsolateral line on the left side, just dorsally of the left gonads; the tunic and mantle had been cut together during the original examination, with the mantle wall still firmly attached to the tunic. The external appearance of the specimen, although somewhat deformed due to the original dissection, remained consistent with the original description (based on a single specimen), as follows: Body proper bluntly pear-shaped, 46 mm long by 30 mm in diameter, with a long (157 mm) 2 mm thick stalk, and approximately 8 short branched root-like processes; tunic surface shagreen-like, densely papillated; tunic often white but mostly irregularly dark brown. The following description of the specimen was made by TN, totally dependent upon a number of photographs taken by NI.

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Holotype Redescription of Culeolus uschakovi

( Fig. 1 View Fig )

Body proper pear-shaped, with proximal end of stalk running posteriad along anterior one-seventh of body mid-ventral line ( Fig. 1A View Fig , Dst). Surface of body proper often white to pale yellow, mostly irregularly dark brown to black ( Fig. 1B View Fig , Bp), entirely bearing low papillae up to 100 to 200 µm base diameter, each mostly filled with opaque roundish matter (white in black or white patches, yellow in pale yellowish patches). A complete ring of prominent conical projections (up to 1.5 mm tall and 0.5 mm in basal diameter) widely encircling atrial aperture obliquely from middorsal to posteroventral margins of body proper ( Fig. 1A View Fig ), most crowded ventrally ( Fig. 1B View Fig ); projections mostly transparent white ( Fig. 1B View Fig ), rarely opaque due to central white matter; containing some or many white to pale yellow opaque spherules, 0.1 to 0.2 mm in diameter; surface without lateral tubercles (in original description; p. 183 and text-fig. 10). Similar conical projections apparent on each side as a dense wide belt from around branchial aperture to proximal end of stalk fused with body proper ( Fig. 1A View Fig ), forming an anteroventral l beard z. No other obvious tunic ridges or projections along ventro- and dorsomedian lines or elsewhere, although some minute cylindrical or bubble-like malformed prominences randomly detectable. Tunic very thin, tough, its inner surface white; mantle very thin, almost transparent, firmly attached to tunic, with body musculature as a sparse network of thin yellow fibers. Part of branchial sac still present, with at least 5 folds on each side, but exact number uncertain due to loss of ventralmost portion; 6–12 longitudinal vessels on each fold, with 1–4 between folds (consistent with original description of 6–11 longitudinal vessels on each fold and intermediate longitudinal vessels 2–4). Digestive system completely detached from mantle, too deformed to determine original configuration; originally described as hepatic appendages on an elongated-oval stomach (p. 184 and text-fig. 12) and with a smooth anal edge (p. 184) confirmed here. Two parallel gonads on each side (as described originally), containing many ovarian eggs (up to ca. 200 µm diameter) and testicular follicles, roughly 2- to 3-lobed ( Fig. 1C View Fig ). Right gonads in tight contact with each other, left gonads separated rather widely from each other, allowing space for occupation by intestine ( Fig. 1C View Fig , Dig) [described as having a simple narrow U-shape in original description]. Heart not found due to damage.

Remarks. The left gonad arrangement, significant for Culeolus taxonomy, was not given in the original description, which stated only that one and a half gonads occurred on each side, the internal (ventral) gonad being shorter than the external (dorsal) one. Clearly, the gonadal number on each side should be regarded as two, the said difference in gonadal length on each side being consistent with the present redescription, illustrated in Fig. 1C View Fig . The original configuration of the two left gonads was reconstructed as described above, the intervening space between the two being considered to have accommodated the simple narrow U-shaped intestine (that is to say, one of the two left gonads was situated inside the intestinal loop). The holotype was originally described as having 16 branchial tentacles, 6 (left) and 5 (right) folds of various heights, stigmata without cilia, and a few horny spicules (simple or having a few short branches) in the longitudinal folds. These last-mentioned features could not be confirmed here due to deterioration of the material.

Taxonomic Considerations on the Validity of C. uschakovi

C. uschakovi was considered to be a junior synonym of C. murrayi Herdman, 1881 by Vinogradova (1970, pp. 498–503), following reexamination of the holotype of the former. However, the supporting description lacked important details, saying only that the holotype of the former was fully consistent with Herdman`s [original] description and 55 specimens of C. murrayi (from deep water in the NW Pacific) in body shape, proportions, and surface texture, the sculpture and structure of the crest [= Culeolus - ridge], and structure of the internal organs, without any reference to gonads. Later, Sanamyan and Sanamyan (2006, p. 333) redescribed part of Vinogradova`s (1970) material, an intact wellpreserved specimen from 5035–5210 m depth in the Chishima (Kurile)- Kamchatka Trench, as having l two gonads on each side z and l on the left, one gonad —— inside and the other outside the gut loop z, and concluded that l We failed to find any reliable feature distinguishing this specimen from C. suhmi and all the specimens of C. murrayi of Vinogradova (1970) and here considered conspecific with C. suhmi z. Accordingly, Sanamyan and Sanamyan (2006) considered C. uschakovi conspecific with C. suhmi Herdman, 1881 , the latter taking precedence, after comparing Redikorzev`s (1941) original description of the former with a newly collected 24 mm long specimen of C. suhmi from 4820 m depth near the Aleutian Trench , emphasizing similarities in l a complete ring of papillae around the posterior end of the body and the two gonads on each side z.

Sanamyan and Sanamyan`s (2006) specimen of C. suhmi , as described (p. 331) and depicted (text-fig. 13A), is clearly similar to the holotype of C. uschakovi in having a complete ring of elongated conical projections widely encircling the atrial aperture on the tunic and being most developed ventrally, its surface furnished wholly with low papillae, many of which included opaque matter. The specimen also had two gonads on each side, with one of the left gonads inside the intestinal loop. However, the authors also noted that l a few separate and relatively long papillae are on the mid-ventral line z, especially between the posteroventral area of the ring towards the atrial aperture, and a similar, although rather insignificant, longitudinal row also detectable posterodorally between the ring and aperture (see their text-fig. 13A) in their C. suhmi specimen, quite unlike the C. uschakovi holotype condition. Furthermore, the anteroventral l beard z of elongated projections along the proximal end of the stalk comprised only a very few (3, according to the figure) large elements in their specimen, such projections being smaller and much more numerous in the aforementioned holotype. These differences may represent intraspecific variations among the NW Pacific populations. However, the type locality of C. suhmi is in the NW Atlantic (3060 m depth), east of New York, North America (see Herdman, 1881, p. 87; 1882, p. 117), a good distance from the NW Pacific locality of C. uschakovi . Also, the holotype of C. suhmi was not fully described, and its gonadal number and arrangement remain unknown. Consequently , conspecificity of these two species should not yet be entertained.

The tunic surface of C. murrayi , originally from the far east off Japan in 4140 m depth, appeared to be quite similar to that of the holotype of C. uschakovi (see Fig. 1A View Fig ), according to Monniot and Monniot`s (1982, p. 117; text-fig. 26) redescription of one of the two syntypes (body proper length 45 mm) of C. murrayi and NT`s reexamination of the other (one of BMNH 1887.7.2.4.29– 30 specimens in the Department of Zoology, The Natural History Museum; the length 49 mm). However, the former 45 mm long syntype had 3 gonads, 1- to 3-lobed, on each side, with one inside the intestinal loop on the left, while the latter 49 mm long syntype had 5 gonads on the left, 1- to 3-lobed, with one inside the loop, but no gonads on the right, thereby differing from the holotype of C. uschakovi (2 gonads on each side). The difference in gonadal number is probably enough to distinguish between the two species.

All in all, C. uschakovi should continue to be treated as a valid species, although future studies, including more detailed morphological information plus molecular data, would be welcome. Thus, the results of the present taxonomic considerations may be summarized as:

Culeolus uschakovi Redikorzev, 1941

( Fig. 1 View Fig )

Culeolus uschakovi Redikorzev, 1941, pp. 183–185 , 211, Pl. 3, fig. 5, text-figs. 10–13.

Culeolus murrayi Herdman, 1881 : Vinogradova, 1970, pp. 498–502, Tab. 3, text-figs. 5–7.

Culeolus suhmi Herdman, 1881 : Sanamyan and Sanamyan, 2006, pp. 331–333, text-fig. 13.