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A new species of coccidian (Apicomplexa: Eimeriidae) from Synaptomys cooperi (Rodentia: Muridae) in Missouri.

ABSTRACT. -- A new species of Eimeria (Apicomplexa: Eimeriidae) was found in the feces and intestinal contents of the southern bog lemming, Synaptomys cooperi Baird, 1858, from St. Charles County, Missouri, USA. Oocysts of this new species are ellipsoidal, 27.7 X 22.1 (24-30 X 17.5-24) [micro]m (N=25); shape index (length/width) 1.26 (1.10-1.53). Micropyle absent; oocyst residuum and polar granule present. Sporocysts are ellipsoidal, 12.6 X 8.6 (10.5-13.5 X 7-9) [micro]m (N=20), with Stieda and substieda bodies; shape index 1.47 (1.39-1.56). Sporozoites each contained a large, ellipsoidal posterior refractile body. This represents the first report of a coccidian from the genus Synaptomys. Key words: Synaptomys cooperi; southern bog lemming; Rodentia; coccidia; Eimeria; Apicomplexa.

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The southern bog lemming is a small vole that occurs in the northeastern portion of North America, extending as far west as Kansas and Nebraska (Linzey, 1983; Linzey and Cranford, 1984). Habitats frequented by bog lemmings are diverse, and studies have suggested the reason for this may be competitive exclusion of Synaptomys by Microtus spp. (Linzey, 1981; 1984). Although no species of coccidia have been described from the genus Synaptomys previously, we recently were able to examine feces and intestinal contents of select specimens. Herein we report the finding of a new species of the genus Eimeria (Apicomplexa).

MATERIALS AND METHODS

Twenty-two southern bog lemmings, Synaptomys cooperi, were collected February-March, 1992 from St. Charles County, Missouri, using Sherman live traps. Animals were transported to the laboratory and euthanized using C[O.sub.2] overdose. Intestinal contents and feces were placed in 2.5% (w/v) aqueous [K.sub.2][Cr.sub.2][O.sub.7] solution and shipped to Kansas State University. Samples were placed in Petri dishes in a shallow layer of [K.sub.2][Cr.sub.2][O.sub.7] solution and allowed to sporulate at room temperature (ca 23[degrees]C) for one week. Oocysts were then concentrated by flotation in an aqueous sucrose solution (specific gravity 1.30), and examined and measured using Nomarski interference-contrast optics. Oocysts were measured using a calibrated ocular micrometer and are reported in micrometers as means, followed by the ranges in parentheses.

RESULTS AND DISCUSSION

Two of 22 (9.1%) of the samples were found to contain coccidian oocysts, which proved to represent the same undescribed coccidian of the genus Eimeria. Below we present a description of the new coccidian.

[FIGURE 1 OMITTED]

TAXONOMIC DESCRIPTION

Eimeria synaptomys new species (Figs. 1-3)

(Apicomplexa: Eimeriidae)

Oocysts ellipsoidal, 27.7 X 22.1 (24-30 X 17.5-24) (N=25); shape index (length/width) 1.26 (1.10-1.53). Wall bilayered, composed of thick, rough outer layer about 1.5 thick and smooth inner layer, about 0.5 thick. Micropyle absent; oocyst residuum present, 5.9 (5-8) (N=20), normally consisting as single homogenous globule but sometimes as 2-many globules enclosed in limiting membrane. Single polar granule present, 2.1 (1.5-2.5) (N=20), occasionally fragmented into two pieces and usually enclosed in membrane surrounding oocyst residuum. Sporocysts ellipsoidal, 12.6 X 8.6 (10.5-13.5 X 7-9) (N=20); shape index 1.47 (1.39-1.56). Wall smooth and single-layered, < 1.0 thick. Stieda body present, covered by thin membrane; substieda body present, small, indistinct, and homogenous. Sporocyst residuum present, consisting as numerous, coarse, homogenous granules 0.5-1.5 in diameter scattered among sporozoites. Sporozoites vermiform, 14.5 X 3.4 (13-16 X 3-3.5) (N=20), arranged head-to-tail in sporocyst. Each sporozoite contains single homogenous posterior refractile body, 5.6 X 3.2 (4-7 X 3-3.5) (N=20); anterior refractile body absent. Nucleus located near center of sporozoites.

[FIGURES 2, 3 OMITTED]

TYPE HOST: Synaptomys cooperi Baird, 1858 ssp. gossii Coues, 1877 "southern bog lemming" (Rodentia: Muridae).

TYPE LOCALITY: St. Charles County, Missouri, 3.4 km West Weldon Spring.

PREVALENCE: 2/22 (9.1%) animals were passing oocysts.

SPORULATION: Unknown. Oocysts were fully sporulated upon arrival at Kansas State University.

LOCATION IN HOST: Unknown. Oocysts recovered from intestinal contents and feces.

ETYMOLOGY: The specific epithet represents the host genus.

REMARKS: Although no species of coccidia have been reported from southern bog lemmings previously, nearly 40 species have been collectively reported from related host genera (i.e. Dicrostonyx, Lemmus, Ellobius, Ondatra, Microtus; see Levine and Ivens, 1990). Of these, only four (all from the genus Microtus) are similar to Eimeria synaptomys new species. Oocysts of E. chetae Arnastauskene, 1980 from M. middendorfi in Russia were reported to lack a Stieda body and discernible sporocyst residuum (Arnastauskene, 1980). Both structures are highly conspicuous in the form we report here. Differences between E. synaptomys new species and E. gomurchaica Veisov, 1963 from Microtus arvalis in Azerbaijan include oocysts of the latter being more spherical, possessing a smooth oocyst wall and a small rather than large sporocyst residuum, and lacking a polar granule (Veisov, 1963). Likewise, oocysts of E. monocrustae Veisov, 1963 from the same host in Azerbaijan are more spherical, do not possess a polar ganule, and also have a highly granular wall with unusual inclusions that form a "zig-zag" appearance (Veisov, 1963). In North America, only E. ochrogasteri Ballard, 1970 from M. mexicanus, M. ochrogaster, and M. pennsylvanicus are similar. Oocysts of this species, however, are smaller and possess an anterior refractile body (Ballard, 1970; Vance and Duszynski, 1985).

LITERATURE CITED

Arnastauskene, T. V. 1980. Characteristics of the infections of small mammals with coccidia in the Taimyr Peninsula in 1974-1975. Tr. Akad. Nauk Liovskoi SSR ser. B, 1980(2):53-60.

Ballard, N. B. 1970. Eimeria ochrogasteri n. sp. from the prairie vole Microtus ochrogaster. J. Protozool., 17:271-273.

Levine, N. D., and V. Ivens. 1990. The Coccidian Parasites of Rodents. CRC Press, Boca Raton. 228 pp.

Linzey, A. V. 1981. Patterns of coexistence in Microtus pennsylvanicus and Synaptomys cooperi. Ph.D. dissertation, Virginia Polytechnic Institute and State University, Blacksburg, 97 pp.

______. 1983. Synaptomys cooperi. Mammalian Species, 210:1-5.

______. 1984. Patterns of coexistence in Synaptomys cooperi and Microtus pennsylvanicus. Ecology, 65:382-393.

Linzey, A. V., and J. A. Cranford. 1984. Habitat selection in the southern bog lemming, Synaptomys cooperi, and the meadow vole, Microtus pennsylvanicus, in Virginia. Can. Field-Nat., 98:463-469.

Vance, T. L., and D. W. Duszynski. 1985. Coccidian parasites (Apicomplexa: Eimeriidae) of Microtus spp. (Rodentia: Arvicolidae) from the United States, Mexico, and Japan, with descriptions of five new species. J. Parasitol., 71:302-311.

Veisov, A. M. 1963. Coccidia in simple field mouse Microtus arvalis Pallas (1778) in Azerbaijan. Izv. Akad. Nauk. Az. SSR ser. Biol. Med. Nauk, 4:61-75.

STEVE J. UPTON AND RICHARD M. PITTS

Division of Biology, Ackert Hall, Kansas State University, Manhattan, Kansas 66506 and ARPERCEN, Attn. OPC, 9700 Page Blvd., St. Louis, Missouri 63132
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Author:Upton, Steve J.; Pitts, Richard M.
Publication:The Texas Journal of Science
Geographic Code:1U4MO
Date:Nov 1, 1993
Words:1126
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