Modest genetic differentiation among North American populations of Sarcocystis neurona may reflect expansion in its geographic range.

Sarcocystis neurona is an important cause of neurological disease in horses (equine protozoal myeloencephalitis, EPM) and sea otters in the United States. In addition, EPM-like disease has been diagnosed in several other land and marine mammals. Opossums are its only definitive hosts. Little genetic diversity among isolates of S. neurona from different hosts has been reported. Here, we used 11 microsatellites to characterize S. neurona DNA isolated from natural infections in 22 sea otters (Enhydra lutris) from California and Washington and in 11 raccoons (Procyon lotor) and 1 striped skunk (Mephitis mephitis) from Wisconsin. By jointly analyzing these 34 isolates with 26 isolates previously reported, we determined that geographic barriers may limit S. neurona dispersal and that only a limited subset of possible parasite genotypes may have been introduced to recently established opossum populations. Moreover, our study confirms that diverse intermediate hosts share a common infection source, the opossum (Didelphis virginiana).

Paramutation alters regulatory control of the maize pl locus.

The maize purple plant (pl) locus encodes a transcription factor required for anthocyanin pigment synthesis in vegetative and floral tissues. The strongly expressed Pl-Rhoades (Pl-Rh) allele is unstable, spontaneously changing to weaker expression states (Pl') at low frequencies and exclusively changing to Pl' in Pl'/Pl-Rh heterozygotes. The weakly expressed Pl' state is mitotically and meiotically stable, yet reversible. This type of allele-dependent, heritable alteration of gene control is called paramutation. Expression studies herein demonstrate that visible differences in anthocyanin pigment levels mirror pl RNA abundance and that pl paramutation is associated with reduced transcription of the pl gene. This transcriptional alteration is accompanied by acquisition of light-dependent regulation. Restriction endonuclease mapping indicates that these changes in pl gene regulation are not associated with detectable DNA alterations or with extensive changes in cytosine methylation patterns. Genetic tests show that Pl-Blotched (Pl-Bh), a structurally similar pl allele encoding an identical pl RNA and PL protein, does not participate in pl paramutation. This result suggests that if cis-acting sequences are required for pl paramutation they are distinct from the protein coding and immediately adjacent regions. A model is discussed in which pl paramutation results in heritable changes of chromatin structure that fundamentally alter regulatory interactions occurring during plant development.

A new Eimeria sP. from the plumbeous Central American caecilian, Dermophis mexicanus (amphibia: gymnophiona) from Volcán Tajumulco, Department of San Marcos, Guatemala.

Fresh fecal samples from 5 caecilians (Dermophis mexicanus) were collected and examined for coccidia in the summer of 1998. The caecilians were collected in the Department of San Marcos, Guatemala. Two of the 5 (40%) specimens of caecilians contained an Eimeria species that is described here as new. This represents the first coccidia described from a gymnophionian host. Sporulated oocysts are spheroidal to subspheroidal, 19.5 X 17.7 (16-23 x 15-21) microm, micropyle and oocyst residuum are absent, and 3 (or more) polar granules are always present. Sporocysts are ovoidal, 11.0 X 7.2 (10-12 x 6-9); a Stieda body and sporocyst residuum are present.

Five new species of Coccidia (Apicomplexa: Eimeriidae) from colubrid snakes of Ecuador.

Fecal samples from 11 colubrid snakes, representing 10 species, collected in Ecuador during October 1994 were examined for coccidian parasites. Feces of 4 individuals, representing 4 host species, contained coccidian oocysts. Three species of Eimeria and 2 species of Isospora were observed and are described here as new. Oocysts of both Eimeria and Isospora were found in the feces of a slug-eating snake, Dipsas vermiculata. Sporulated oocysts of the Eimeria sp. are spheroid to subspheroid, 16.7 by 16.6 microm (14-18 by 14-18 microm) and those of the Isospora sp. are spheroid and 15.0 microm (13-18 microm) in diameter. Imantodes cenchoa, the common bluntheaded treesnake, was infected with a species of Eimeria. These sporulated oocysts are ellipsoid, 23.3 by 16.2 microm (25-21 by 15-17 microm). Sporulated eimerian oocysts from Leptodeira annulata, the southern cat-eyed snake, are subspheroid, 22.5 by 18.8 microm (19-26 by 17-21 microm). Feces of a juvenile Imantodes lentiferus, the bluntheaded vine snake, contained ovoid to ellipsoid isosporan oocysts, which measured 21.6 by 15.0 microm (20-23 by 14-16 microm) when sporulated.

Seven new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from colubrid snakes of Guatemala and a discussion of what to call ellipsoid tetrasporocystic, dizoic coccidia of reptiles.

During a survey of Guatemalan herpetofauna in the summers of 1998-2000, 29 presumed new species of Eimeria Schneider, 1875 were found, seven of which have a distinct elongate-ellipsoidal shape (L/W ratio >or= 1.7) and are described herein. Six of the seven new species are similar in oöcyst length, width and L/W ratio and sporocyst length, width and L/W ratio, lack a micropyle, oöcyst residuum, Stieda body, sub-- and parastieda bodies, have a polar granule and sporocyst residuum, and their sporocysts appear to have dehiscence sutures. The seventh is slightly smaller and has sporocysts with a Stieda body. The new species are: E. coniophanes n. sp - whose sporulated oöcysts from Coniophanes fissidens are 29.2x14.9 (27-31x13-16) microm, with sporocysts 10.0 x 7.8 microm; E. coniophis n. sp. -from Conophis lineatus are 32.0x16.5 (30-34x14-18) microm, with sporocysts 10.2 x 8.9microm; E. dryomarchoni n. sp. - from Drymarchon corais are 32.2x17.7 (31-34x17-19) microm, with sporocysts 10.7 x 8.6 microm; E. leptophis n. sp. - from Leptophis mexicanus are 29.5x17.0 (28-31x16-18) microm, with sporocysts 10.0 x 9.1 microm; E. oxybelis n. sp. - from Oxybelis aeneus are 31.8x16.5 (29-33x15-18) microm, with sporocysts 10.3 x 8.8 microm; and E. scaphiodontophis n. sp. - from Scaphiodontophis annulatus are 30.0x15.3 (28-33x14-16) microm, with sporocysts 9.9 x 7.9 microm. Sporulated oöcysts of E. siboni n. sp. from Sibon nebulata are 24.3x14.2 (21-27x13-16) microm, with sporocysts 10.0 x 7.1 microm and with a Stieda body. We conclude that until all aspects of each life-cycle are known, it is prudent at this time to name all tetrasporocystic dizoic coccidia from snakes as members of Eimeria rather than place some of them in Choleoeimeria Paperna & Landsberg, 1989.