Collastoma kozloffi sp. n., a Neorhabdocoel Turbellarian from the Intestine of the Sipunculan Themiste dyscrita

Abstract

Collastoma kozloffi sp. n. is described from the intestine of the sipunculan, Themiste dyscrita, collected at three localities on the Oregon coast. This species is particularly distinctive because of its large egg capsule (length about 400-500 ,m). The relationships of the five known species of Collastoma are discussed. The gut-inhabiting rhabdocoels of the genus Collastoma are restricted to worms of the phylum Sipuncula. The genus was established by Dorler (1900) for C. monorchis, found in Golfingia vulgaris (=Phascolosoma vulgare) at Roscoff, France. Wahl (1906) mentioned a species taken from Phascolosoma granulatum (=Phymosoma granulatum), and the legend for his illustrations refer to this worm as C. minuta. Later (1910b), he provided a proper description, emending the name to C. minutum. A third species of Collastoma was described from Golfingia eremita (=Phascolosoma eremita) by Beklemishev (1916). Considerably later, Kozloff (1953) described C. pacifica, found in Themiste pyroides (=Dendrostoma pyroides), at Pacific Grove and Carmel Point, Monterey Co., California. I have found this species in T. pyroides at Sunset Bay, Coos Co., Oregon. The current names for the sipunculan hosts of the various species of Collastoma referred to above are those given by Stephen and Edmonds (1972). Collastoma belongs to the family Umagillidae, and is the only genus in the subfamily Collastominae, as established by Wahl (1910a). Its placement in this subfamily is based primarily on the presence of a single, median testis, instead of two lateral testes. The question of subfamilial division of the Umagillidae has been dealt with by Stunkard and Corliss (1951). In the course of examination of various sipunculans along the Pacific coast in 1958, I found a new species of Collastoma in TheReceived 23 July 1980; revised 4 November 1980; accepted 17 November 1980. miste dyscrita collected at Ecola State Park, Tillamook Co., Oregon. An additional 50 individuals of the host species were obtained at Cape Arago and Sunset Bay, Coos Co., Oregon in 1959. Of these, 24 had this new Collastoma. The number of worms in a single host ranged from one to 103. MATERIALS AND METHODS The description is based on specimens fixed in Bouin's fluid or Brasil's fluid. The worms were not flattened during fixation. Whole mounts were stained with borax carmine. Specimens used for sections were embedded in paraffin, cut serially at 5 or 8 /um, and stained with iron hematoxylin. Collastoma kozioffi sp. n. (Figs. 1-6)