The Genus Schizorchis (Cestoda: Anoplocephalidae) in Eurasian Pikas, Ochotona spp. (Lagomorpha: Ochotonidae), with Descriptions of New Species

Abstract

Pikas, Ochotona hyperborea (Lagomorpha: Ochotonidae), were collected at six localities in northeastern Siberia (Magadansk Oblast') and examined for helminths. Cestodes of the genus Schizorchis (Anoplocephalidae) were found at two localities. Schizorchis yamashitai is reported for the first time from the Eurasian continent, and S. ryzhikovi n. sp. is described. In addition, S. nepalensis n. sp. is described from 0. roylei in Nepal. The relationships and zoogeography of these cestodes are discussed. The mammalian genus Ochotona Link (Lagomorpha: Ochotonidae) is represented in the Nearctic by two species, and in the Palaearctic by approximately 17 (cf. Honacki et al., 1982). As a group, pikas have a distinctive helminth fauna, composed mainly of host-specific genera. Of three such genera of cestodes, only one, Schizorchis Hansen, 1948, is known to be polytypic, with two species each in North America and Eurasia. One palaearctic species, S. yamashitai Rausch, 1963, is known only from Ochotona hyperborea (Pallas) on the island of Hokkaido. The second, S. altaica Gvozdev, 1951, has been reported from pikas of various species on the Eurasian continent. However, discrepancies in the descriptions of cestodes identified as S. altaica suggest that more than one species is involved. Fieldwork undertaken by us in northeastern Siberia during four years (197577 and 1979) provided the opportunity to collect pikas at various localities, and from these animals, we obtained cestodes representing two species of Schizorchis. The availability of additional comparative material permitted a reassessment of taxa occurring in Eurasian pikas, including cestodes from Ochotona roylei (Ogilby), from Nepal, identified tentatively by Rausch & Ohbayashi (1974) as S. altaica. The results of this work are reported in the present paper, and two additional species of Schizorchis are described. 1 Publication costs, in part, are being met by a grant from the Spencer-Tolles Fund of the American Microscopical Society. 2 Fieldwork in northeastern Siberia was carried out under the U.S.A./U.S.S.R. Environmental Protection Treaty, Area V, Subproject A-3, Diseases and Parasites of Wildlife. Logistic support in the Soviet Union was provided by the Institute of Biological Problems of the North, Far-Eastern Scientific Center, Academy of Sciences of the U.S.S.R., Magadan, under the direction of Dr. V. L. Kontrimavichus. 3 Present address: Gor'kii Institute of Veterinary Research, Gor'kii N2, U.S.S.R. TRANS. AM. MICROSC. Soc., 103(2): 144-156. 1984. ? Copyright, 1984, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.159 on Fri, 09 Dec 2016 05:19:02 UTC All use subject to http://about.jstor.org/terms VOL. 103, NO. 2, APRIL 1984 MATERIALS AND METHODS With the exception of the specimens from Ochotona roylei, which had been preserved in situ, the cestodes were allowed to relax in water, fixed in a hot solution of 10% formalin, stained in acetic carmine or hematoxylin, dehydrated, and cleared in terpineol. After removal to xylene, the tegument and underlying muscle layers were removed from part or all of one strobilar surface of selected specimens, which then were mounted permanently. Also, some previously mounted cestodes were removed from the slides, rehydrated and restained if necessary, and similarly processed. Comparative material consisted of the following: Schizorchis ochotonae Hansen, 1948 from Ochotona princeps (Richardson), near Jackson, Wyoming, 2; S. altaica Gvozdev, 1951 from 0. rutila (Severtsov), Kazakhstan (leg. E. V. Gvozdev), 2; S. caballeroi Rausch, 1960 from 0. collaris (Nelson), various localities in Alaska, 20, and from 0. princeps, Lane County, Oregon (leg. C. Maser), 2; and S. yamashitai Rausch, 1963 from 0. hyperborea, Lake Shikaribetsu, Hokkaido, 7.