p. 76-81, figs. 1-3 in: Polychaeta and Their Ecological Significance. Explorations of the Fauna of the Seas 43 (51), Zoological Institute, Russian Academy of Sciences, St. Petersburg.
[ Translated April 1995 by Dr. Alexander V. Verashchaka, P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow. [A.V.V. translation of Russian title] Translation provided by Mary Petersen, Zoological Museum, University of Copenhagen.]
In the summer of 1990 small shiny brown worms of the genus Orbiniella were found among rhizoids of small algae in the littoral zone of Bering Island. The genus belongs to the subfamily Protoariciinae, members of which have been found for the first time in the northwest part of the Pacific Ocean. Several specimens of Orbiniella from the littoral zone of Medniy Island (Komandorskie Islands) were given by V. Gulbin (Institute of Marine Biology, Vladivostok), and one specimen was found by me in the littoral zone of Shikotan Island (Kurile Islands). In the world ocean fauna, 5 species of Orbiniella are known: O. minuta Day, 1954 (type species); O. uniformis Hartman, 1967; O. drakei Hartman, 1967; O. branchiata Hartman, 1967; O. nuda Hobson, 1974, but only O. uniformis and O. nuda are similar to the type species in the main characters. In O. drakei the body is divided into thorax and abdomen, and parapodia are well developed, which is not characteristic for the genus. As to O. branchiata, where the body is also divided into thorax and abdomen, this species is unique among all orbiniids in having not two but three anterior segments lacking setae. Judging by the generic diagnosis given by Fauchald and Solis-Weiss (Fauchald, 1977; Solis-Weiss, Fauchald, 1989), the mentioned species is not included in the genus Orbiniella. Probably Falklandiella annulata Hartman belongs to the genus Orbiniella. According to the description (although not complete enough), this species replaces O. uniformis, differing only in the absence of eyes (Hartman, 1967). The characteristics of the genus Orbiniella modified as compared to the diagnosis of Day, Solis-Weiss and Fauchald (Day, 1954; Solis-Weiss and Fauchald, 1989) are as follows:
Body not divided into thorax and abdomen, head lobe round or bluntly conical. Eyes present or absent. First and second segments without parapodia and setae. Podial lobes not developed. Branchiae absent. Setae simple. Dorsal setae either with wide teeth along the margins or with transverse rows of spines, or with both; sometimes teeth bearing long hairs at distal tips; smooth hairlike setae also found. Ventral setae hairlike and cirrate as in the dorsal parapodial ramus, and strong, short, acicular setae. Pygidium two-lobed, without anal cirri. Anus terminal. Worms small, 3-12 mm long; up to 36 setigers. Genital products created only in several segments. Type species: Orbiniella minuta Day, 1954. Remarks. Solis-Weiss and Fauchald used in the diagnosis such characters as division of body into thorax and abdomen through transitional segments, and presence of furcate setae. The first character is characteristic only for O. drakei, strongly differing from the type species. The second character is found in branchiata, a species which the authors themselves do not refer to the genus Orbiniella.
D e s c r i p t i o n. Small worms, 12 mm long, 0.8 mm wide, with 28-32 setose segments. Segments separated clearly. Cephalic lobe round, two small black eyes deeply under the cuticle (Fig. 1). Pharynx soft, saclike, wrinkled. Body not divided into thorax and abdomen. Podial rami not developed. Two anterior segments without setae. Dorsal setae hairlike: 1-5 smooth setae found in bundle of setae, 2-4 nonplumose and 1-7 plumose cirrate setae with teeth bearing hairs (Fig. 2). 2-4 (seldom 5) slightly curved hooklike setae and 2-4 cirrate hairlike setae (may be absent in some segments), and 1-2 plumose cirrate setae (sometimes found in the anterior segments, Fig. 2) are usually found in the ventral bundle. Pygidium with two round lobes. Anus terminal. Live worms dark brown, lighter ventrally; two dark orthogonal spots on dorsal side of each segment in anterior part of body. Two large brown spots at posterior margin of cephalic lobe. Color often remains after fixation (Fig. 1). 18 and 25 July 1990 females were found containing oval eggs, 225 um x 250 um, in the body cavity, and 29 July 1990 there were found males with active pearlike spermatozoids in the spermatophores (Fig. 3). Remarks: O. plumisetosa is distinguished from the othere species in the presence of setose cirrated and smooth setae and in the body color. It is most closely related to O. nuda. The specimen from the Shikotan Islands is in bad condition; I haven't found setose cirrate setae in this, therefore its identity with O. plumisetosa is questionable.
Fauchald, K. 1977. The Polychaete worms definitions and keys to the Orders Families and Genera. -- Nat. Hist. Mus. Los Angeles County Sci. Ser. 28: 188
Hartman, O. 1967. Polychaetous annelids collected by the USNS Eltanin and Staten Island Cruises, chiefly from Antarctic Seas. -- Allan Hancock Found., Los Angeles. 387
Hobson, K. 1974. Orbiniella nuda new species (Orbiniidae) and nine new records of other sedentariate polychaetous annelids from Washington and British Columbia. -- Can. J. Zool. 52 (1): 69-75.
Solis-Weiss, V. & K. Fauchald. 1989. Orbiniidae (Annelida: Polychaeta) from mangrove root-mats in Belize, with a revision of Protoariciin genera. -- Proc. Biol. Soc. Wash. 102 (3): 772-792.
G. N. Buzhinskaja , Zoological Institute, Russian Academy of Sciences, St. Petersburg, 199034, Russia
Fig. 2. Orbiniella plumisetosa sp. n.: A - first parapodium; B - parapodium, posterior segments; V - plumate crenulated seta, first setiger; G - crenulated seta, XVIII setiger; D - acicular seta. XXIV setiger; E - smooth capillary seta. XVIII setiger.
Fig. 3. Orbiniella plumisetosa sp. n., spermatophore and form of sperm.