Asinus

Abstract: Rice yellow mottle virus (RYMV), endemic in Africa, is believed to be spread by chrysomelid beetles, although the infections in a field often cannot be explained by the prevailing number of beetles. We show that the grass rat Arvicanthis niloticus, domestic cows (Bos spp.), and donkeys (Asinus spp.) are potent and efficient transmitters of RYMV. Spread of RYMV by rats was demonstrated in cage experiments wherein individual rats transmitted the virus from healthy to infected rice plants and confirmed in a field experiment. Experiments with cows and donkeys showed that they could transmit the virus in plots with healthy and infected plants and to plots with healthy plants. A high percentage of seedlings became infected when a cow grazed in a seedbed after being fed with infected rice plants. Transmission also was observed when cows were allowed to graze on the stubble of infected fields. The disease incidence increased at least fourfold over time to approximately 36% of the plants infected in the experimental plots of two stubble fields. The results obtained in these stubble fields suggest that cattle-mediated spread will enhance the size of the virus load in the contraseason and the infection potential to infect the next crop.

Abstract: Ten species of Pleistocene mammals are represented in a collection of fossils from a placer mining site at Lost Chicken Creek. Among these are four extinct species, an extinct subspecies, two species now extinct in the region, and three species that still occupy the area. Bison crassicornis (large-horned bison), Equus (Asinus) lambei (Yukon wild ass), and Rangifer tarandus (caribou) remains are commonest. Equus (Asinus) cf. kiang (kiang-like wild ass) is recorded for the first time from Alaska.These mammals seem to have occupied a cool steppe-like grassland during late Wisconsin time. Bones of horse, wapiti, bison, and helmeted muskox (Symbos) have yielded radiocarbon dates between 27 000 and 10 000 years BP. The dated bison bone was modified by man, indicating that people were present, and probably hunting and butchering bison, in easternmost Alaska at the close of the Wisconsin glaciation.

Abstract: Existing data indicate that a greater preponderance of adult females rather than adult males occurs in most species of mammals. The hypothesis that such differences arise as a result of intermale reproductive competition for females (and not predation) was examined in the Equidae by comparing populations of horses (Equus caballus), asses (E. asinus), and two species of zebras (E. zebra and E. burchelli) in predator-free, predator-rich and insular ecosystems. Evidence is presented that: (1) sex differences in adult mortality occur; (2) they relate to the type and intensity of natural predation; and (3) asymmetries in sex ratios are most often explicable in terms of intermale reproductive competition. Exceptions are discussed and they are complicated by numerous proximate factors.

Abstract: The full extent of the polymorphism of ELA-DRA in Equidae is not yet known. Given the apparent differences in DRA polymorphisms between Equidae and other species, the aims of this study were to more fully characterize ELA-DRA, determine the extent of gene polymorphism and establish the allele-frequency distribution. An allele reference panel for the second exon of ELA-DRA was established by sequence-based typing of 69 equine DNA samples consisting of various breeds of domestic horse (Equus caballus), together with donkeys (Equus asinus), Grant's zebras (Equus boehmi) and one onager (Equus hemionus). Five of the six previously reported alleles detected using single-strand conformation polymorphism were found: ELA-DRA*0101, ELA-DRA*0201, ELA-DRA*0301, ELA-DRA*0501 (Albright-Fraser DG et al. Polymorphism of DRA among equids. Immunogenetics 1996: 43: 315-7) and ELA-DRA*0601 (GenBank accession number AF5419361). In addition to the previously reported alleles, five novel ELA-DRA alleles were detected within the ELA-DRA allele reference panel. One of these was identified in E. caballus (ELA-DRA*JBH11), one in E. boehmi and E. hemionus (ELA-DRA*JBZ185) and three in E. asinus (ELA-DRA*JBD3, ELA-DRA*JBD17 and ELA-DRA*JBH45). A total of 565 equine DNA samples were screened using reference-strand-mediated conformation analysis, a double-stranded conformation-based mutation detection system that can be used to type existing ELA-DRA alleles and identify new variants. Based on our findings, at least 11 ELA-DRA alleles are now known to exist, and this level of polymorphism at the DRA locus appears to be unique to the genus Equus. Both the previously reported alleles and the new alleles displayed a species-specific distribution.