Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

MATERIALS AND METHODS Between 1984 and 1992, 66 O. daurica were collected and examined for helminths in Mongolia. Daurian pikas were trapped at 10 localities, namely: Davaany zorlog, Jargalant, Burdiin Els in Tov province; Mt Tarvagatain nuruu in Arhangai province; Bat-Olzii county in Ovorhangai province; Mt Bogd uul near Ulaan Baataar city; Borig Deliin Els in Zavhan province; Bulgan county in Hovd province; Holonbuir county in Dornod province; and Hanh county in Hovsgol province. All pikas were shot or trapped. The collections were made during the summer, from June to August. The captured mammals were dissected and examined for helminths either immediately or later, after preservation in 10% formalin solution. The digestive system, lungs, body cavity and subcutaneous tissues were checked for helminths. Larval cestodes and nematodes were fixed and preserved in 10%> formalin. These were cleared in glycerol or lactic acid, after which a rostellum of each larva was mounted in Hoy er'

s medium separately from the cyst. Adult cestodes were fixed in 70% alcohol, stained with Schneider's aceto-carmine, dehydrated in an ethanol series, cleared in cedar oil, and mounted in Canada balsam. All measurements were taken with the help of a video micrometer. RESULTS The larvae of T. rétracta were found in one out of the 66 examined O. daurica (prevalence: 1.52%, intensity: 18 specimens) in Borig Deliin Els in Zavhan province (north-western part of Mongolia). Besides the T. rétracta larvae, seven other helminths were identified in Daurian pika: D. spasskii, S. altaica, C. andrejevi, D. schumakowitchi, L. vesicularis, G. olsoni and Trichuris sp. Description of Taenia rétracta Linstow, 1803 larvae (Figs 1-3.) The following description is based on six specimens. The larvae were situated freely without cyst, in the peritoneal cavity of the host. They are elongated in shape and whitish in colour. The anterior end of the larvae is pseudosegmented with invaginated or evaginated scolex. The posterior end consists of a relatively large bladder, which is filled with liquid, and possesses an attenuated appendage. Total length of larvae ranges from 6.7 to 14 mm (mean: 11.2 mm). Width is 2.25 mm with a range of 1.8 to 3.1 mm. The scolex has four suckers and is 1.141 mm in diameter (0.976-1.345). The mean diameter of suckers is 0.319 mm (0.260-0.380). The rostellum is armed with two rows of characteristically shaped hooks, 34-38 in number. The length of Fig. 1. The larvae of Taenia rétracta large hooks ranges from 0.266 to 0.314 mm Linstow, 1803. Scale bar: 5 mm.