Eimeria from Jumping Mice (Zapus spp.): A New Species and Genetic and Geographic Features of Z. hudsonius luteus

Abstract

Of 103 jumping mice (Zapus spp.) examined, 29 (28.2%) had coccidian oocysts in their feces: one of seven (14%) Z. trinotatus eureka from Humboldt Co., California; 25 of 60 (42%) Z. princepsprinceps, including seven of 18 (39%) from Boulder Co., Colorado, and 18 of 42 (43%) from Santa Fe and Taos cos., New Mexico; and three of 36 (8%) Z. h. luteus, including one of one from Sandoval Co., New Mexico, two of 13 (15%) from Apache Co., Arizona, and none of 22 from Otero and Soccoro cos., New Mexico. Twenty-eight of 29 infected mice had only Eimeria zapi oocysts in their feces; the only Z. h. luteus from Fenton Lake, Sandoval Co., New Mexico, had oocysts of a species which we describe here as new. Sporulated oocysts of Eimeria hudsonii sp. n. from Z. h. luteus are elliptical, 20.9 X 14.4 (18-23 X 13-16) ,um with ovoid sporocysts 10.5 X 5.6 (8-11 X 57) gm. A micropyle cap, polar and substieda bodies were absent, but a micropyle, oocyst and sporocyst residua, and Stieda body were present. Sporozoites have one large posterior refractile body. The oocyst wall has two layers. This is only the second eimerian reported from Zapus spp. The geographic distribution of E. zapi closely paralleled genetic and geographic features recently reported within the host taxon Z. h. luteus. Since May 1979, we have collected and examined over 3,000 wild mammals from the United States, northern Mexico, Baja California, and Japan. These collections are part of a continuing study designed to understand the evolutionary relationships of certain groups of congeners and conspecifics using pelage, skeletal, morphologic, electrophoretic, karyotypic, and parasite data. Ultimately we hope to be able to relate host genetics and distribution to susceptibility, parasite burdens, and coccidian specificity. This report is the first on the coccidians of one group of these mammals. We examined four species of Zapus from four states for Coccidia and found two eimerians, Eimeria zapi Gerard, Chobotar, and Ernst, 1977, and a form which we describe here as new. MATERIALS AND METHODS Hosts were killed within a few hours after being live trapped. The abdominal cavity was opened by a longitudinal ventral incision and the intestinal tract, from the duodenum to the anus, was removed. The small intestine was slit lengthwise and placed into a vial of AFA (Humason, 1979) to preserve helminths. The cecum and colon were slit lengthwise and preserved, with their contents, in vials containing 2.5% aqueous (w/v) K2Cr207. Upon return to the laboratory all vials were refrigerated (4 C) until they could be processed and examined. Processing for oocysts consisted of separating fecal contents from cecal-colon tissue by scraping with a scalpel. The fecal-K2Cr207 mixture from each mouse was placed at 23 C for 7 days in a 15-cm Petri dish. Received 28 September 1981; revised 6 January 82, 24 May 1982; accepted 6 June 1982. It was then filtered through 40and 60-mesh brass screens and aliquots of the filtrate were examined by coverslip flotation with a concentrated sucrose solution (sp. gr. 1.15). Oocysts were measured with an ocular micrometer and photographed with either Panatomic-X or Ilford Pan F 35-mm film within a Zeiss Universal Photomicroscope equipped with both brightfield (Neofluar) and Nomarski-interference XI 00 objectives. All measurements are in ,um with the ranges in parentheses following the means.