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A new species of Eimeria (Apicomplexa: Eimeriidae) from Pseudemys texana (Testudines: Emydidae), from north-central Texas.

ABSTRACT. -- A new species of coccidian is described from a Texas river cooter, Pseudemys texana, from north-central Texas. Oocysts of the new species are slightly pear-shaped, 21.2 X 16.1 (16.8-23.2 X 13.6-17.2) [micro]m (mean, range), with a smooth, thin, single-layered wall; shape index (length/width) 1.3 (1.2-1.4). A micropyle is absent but an oocyst residuum and occasionally, a polar granule, are present. Sporocysts are elongate, 12.8 X 6.5 (10.6-14.4 X 6.2-7.2) [micro]m, with a smooth, thin, single-layered wall; shape index 2.0 (1.7-2.3). An elaborate dome-shaped Stieda body resembling Die Pickelhaube (spike of a German World War I helmet); buttonlike process at end of sporocyst opposite the Stieda body. Spherical sporocyst residuum present but often scattered or composed of cluster of large granules, rarely membrane bound. Sporozoites are elongate, 11.7 X 3.1 (10.4-12.8 X 2.6-3.4) [micro]m, arranged head-to-tail within the sporocyst and containing anterior and posterior refractile bodies. A nucleus lies between the refractile bodies. In addition to the type host, oocysts of the new taxon were collected from a Missouri River cooter, P. concinna metteri, from central Arkansas. Key words: Eimeria; new species; coccidia; river cooter; Texas.


The Texas river cooter, Pseudemys texana Baur, 1893, is a large, basking emydid turtle that ranges from north-central Texas southward to the Gulf of Mexico (Conant and Collins, 1991). The species prefers rivers and tributaries but occasionally inhabits ditches and cattle tanks. In addition to providing a summation of the coccidian parasites of turtles, McAllister and Upton (1989) reported two new species of Eimeria from P. texana. Since that time, an additional undescribed eimerian was found in P. texana and a Missouri River cooter, P. concinna metteri Ward, 1984, that we describe herein as new.


Individual adult female Pseudemys texana and P. concinna metteri were collected alive by hand from Somervell County, Texas, and Garland County, Arkansas, respectively, and their feces examined for coccidian parasites. Methods for processing, concentrating, measuring, and photographing coccidia have been previously described (McAllister and Upton, 1989). All measurements were made with a calibrated ocular micrometer and are reported in micrometers ([micro]m) as means, followed by the ranges in parentheses. Oocysts of the new species were nine days old when measured and photographed.


Both turtles were found to be passing coccidian parasites, including a new species of Eimeria. Pseudemys texana also harbored E. pseudemydis Lainson, 1968, and P. c. metteri was also infected with E. marginata (Laveran and Mesnil, 1902) Doflein, 1909, and E. trachemydis McAllister and Upton, 1988. Comparisons were made with measurements of other coccidians reported previously from turtles (McAllister and Upton, 1989) and a description follows of the new species we observed.


Eimeria somervellensis, new species

(Figs. 1-4)

Oocysts slightly pear-shaped, 21.2 X 16.1 (16.8-23.2 X 13.6-17.2) (N = 30), with smooth, thin, single-layered wall, ca. 0.8 thick; shape index (length/width) 1.3 (1.2-1.4). Single polar granule occasionally present, attached either to oocyst residuum or sporocyst; micropyle absent. Spherical oocyst residuum, 5.9 (4.8-7.2), with vacuole and coarse granules. Sporocysts elongate, 12.8 X 6.5 (10.6-14.4 X 6.2-7.2), with smooth, thin, single-layered wall about 0.3-0.4 thick; shape index 2.0 (1.7-2.3). Elaborate dome-shaped Stieda body present, resembling Die Pickelhaube (spike on the German World War I helmet), 1.6 X 2.1 (1.0-2.0 X 1.8-2.4); buttonlike process present at end of sporocyst opposite Stieda body. Faint substieda body present but parastieda body absent. Spherical sporocyst residuum present, 3.0 (2.4-4.0) (N = 20), often scattered or composed of cluster of large granules, rarely membrane bound. Sporozoites elongate, 11.7 X 3.1 (10.4-12.8 X 2.6-3.4) (N = 20) in situ, arranged head-to-tail within sporocyst. Each sporozoite contains spherical or ovoid anterior refractile body, 2.2 wide X 2.3 long (2.0-2.4 X 2.0-3.0) (N = 20), and spherical or ovoid posterior refractile body, 2.9 wide X 3.5 long (2.4-3.2 X 2.6-4.8) (N = 20). A nucleus lies between refractile bodies.


Type host. -- Pseudemys texana Baur, 1893, Texas river cooter (Testudines: Emydidae), adult female, C. T. McAllister no. 890611-5, collected on 11 June 1989 (released).

Type specimens. -- Syntypes (oocysts in 10 percent formalin) are deposited in the U.S. National Museum, Beltsville, Maryland 20705 as USNM 80865.

Type locality. -- Texas, Somervell County, 14.5 km. NW Glen Rose off county road 308 at Georges Creek.

Other host. -- Pseudemys concinna metteri Ward, 1984, Missouri river cooter, adult female, C. T. McAllister no. 910528-1, obtained on 28 May 1991, voucher deposited in the Arkansas State University Museum of Zoology as ASUMZ 17888.

Other locality. -- Arkansas, Garland County, 4.0 km. N Bear at Brady Mountain Recreation Area, Lake Ouachita.

Sporulation. -- Endogenous. Oocysts recovered from feces and intestinal contents were fully sporulated.

Site of infection. -- Unknown. Oocysts were recovered from feces and intestinal contents.

Prevalence. -- One of nine (33 percent) P. texana examined (includes McAllister and Upton's 1989 study of eight P. texana) and one of one P. c. metteri.

Etymology. -- The nomen triviale combines the name of the county in Texas from which the type host was collected and -ensis (L., belonging to).


Eimeria somervellensis most closely resembles E. marginata from western painted turtles, Chrysemys picta bellii, map turtles, Graptemys geographica, and false map turtles, G. pseudogeographica, from Iowa (Deeds and Jahn, 1939; Wacha and Christiansen, 1976), and red-eared sliders, Trachemys scripta elegans, from Texas (McAllister and Upton, 1988). However, sporocysts of the new species are less robust and the Stieda body is more elaborate than in E. marginata. Other similar species include E. chrysemydis (Deeds and Jahn, 1939) Wacha and Christiansen, 1976, from C. p. bellii, from Iowa, and T. s. elegans (McAllister and Upton, 1988, 1989) and Cagle's map turtles, G. caglei, from Texas (McAllister et al., 1991), and E. megalostiedai Wacha and Christiansen, 1974 from wood turtles, Clemmys insculpta, from Iowa (Wacha and Christiansen, 1974), but oocysts of E. somervellensis are much larger and smaller, respectively.


The senior author thanks the Texas Parks and Wildlife Department and the Arkansas State Game and Fish Commission for Scientific Collecting Permits nos. SPR-0390-027 and 775, respectively. Ms. Shirley A. Campbell, Medical Librarian, VAMC-Dallas, kindly provided information on Die Picklehaube.


Conant, R., and J. T. Collins. 1991. A field guide to reptiles and amphibians of eastern and central North America. Houghton Mifflin Co., Boston, 3rd ed., 450 pp.

Deeds, O. J., and T. L. Jahn. 1939. Coccidian infections of western painted turtles of the Okoboji region. Trans. Amer. Micros. Soc., 58:249-253.

McAllister, C. T., and S. J. Upton. 1988. Eimeria trachemydis n. sp. (Apicomplexa: Eimeriidae) and other eimerians from the red-eared slider, Trachemys scripta elegans (Reptilia: Testudines), in northcentral Texas. J. Parasitol., 74:1014-1017.

_____. 1989. The coccidia (Apicomplexa: Eimeriidae) of Testudines, with descriptions of three new species. Canadian J. Zool., 67: 2459-2467.

McAllister, C. T., S. J. Upton, and F. C. Killebrew. 1991. Coccidian parasites (Apicomplexa: Eimeriidae) of Graptemys caglei and Graptemys versa (Testudines: Emydidae) from Texas. J. Parasitol., 77:500-502.

Wacha, R. S., and J. L. Christiansen. 1974. Eimeria megalostiedai sp. n. (Protozoa: Sporozoa) from the wood turtle, Clemmys insculpta, in Iowa. Proc. Helminthol Soc. Washington, 41:35-37.

_____. 1976. Coccidian parasites from Iowa turtles: systematics and prevalence. J. Protozool., 23:57-63.


Renal-Metabolic Laboratory (151-G), Department of Veterans Affairs Medical Center, 4500 S. Lancaster Road, Dallas, Texas 75216, and Division of Biology, Ackert Hall, Kansas State University, Manhattan, Kansas 66506
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Author:McAllister, Chris T.; Upton, Steve J.
Publication:The Texas Journal of Science
Geographic Code:1U7TX
Date:Feb 1, 1992
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