Sperm of the mouse, M us musculus, was X-irradiated in vitro before fertilization. Dosages were between 100 and 50 000 r. With increasing irradiation of the sperm, the chromosome complement of embryos, scored at 3ijr days’ gestation, declined from diploid to haploid. Higher dosages increasingly retarded embryonic development, 30000 and 50 000r restricting development to the first cleavage. Gyno...

Diploid gynogenesis was induced in muskellunge Esox masquinongy using UV-irradiated muskellunge sperm as the first step in producing monosex females. In this approach, we have to rely on negative controls as an indirect reference for sperm genetic material destruction. In the first experiment, equal proportions of gynogenetic females and males were produced. Negative controls, UV-irradiated spe...

Unisexual sperm-dependent vertebrates are of hybrid origins, rare, and predicted to be short-lived as a result of several challenges arising from their mode of reproduction. In particular, because of a lack of recombination, clonal species are predicted to have a low potential to respond to natural selection. However, many unisexual sperm-dependent species persist, and assessing the genetic div...

ABOUT one percent of the 3,000 species of lizards in the world have all-female populations in which reproduction seems to be by true parthenogenesis (as opposed to gynogenesis or hybridogenesis). For some species, no males have ever been found at any localities. For a few species, all-female populations occur at some localities, bisexual populations at others. (In unisexual populations all norm...

Distinguishing between hybrid introgression and incomplete lineage sorting causing incongruence among gene trees in that they exhibit topological differences requires application of statistical approaches that are based on biologically relevant models. Such study is especially challenging in hybrid systems, where usual vectors mediating interspecific gene transfers--hybrids with Mendelian hered...

Unisexual (all female) salamanders in the genus Ambystoma are animals of variable ploidy (2N-5N) that reproduce via a unique system of 'leaky' gynogenesis. As a result, these salamanders have a diverse array of nuclear genome combinations from up to five sexual species: the blue-spotted (A. laterale), Jefferson (A. jeffersonianum), smallmouth (A. texanum), tiger (A. tigrinum) and streamside (A....

Silver crucian carp (Carassius auratus gibelio) is a unique triploid bisexual species that can reproduce by gynogenesis. As all other gynogenetic animals, it keeps its chromosome integrity by inhibiting the ®rst meiosis division (no extrusion of the ®rst pole body). To understand the molecular events governing this reproduction mode, suppression subtractive hybridization was used to identify th...

The Amazon molly Poecilia formosa is a gynogenetic fish that reproduces through the development of ameiotic diploid eggs triggered by insemination by males of related species without following karyogamie. This leads to clonal offspring. In rare cases, however, this gynogenesis is leaky, and paternal DNA in the form of small supernumerary chromosomes is included into the maternal genome. We have...

Although most vertebrates reproduce sexually, a small number of fishes, amphibians and reptiles are known in which reproduction is asexual, i.e. without meiotic recombination. In fishes, these so-called unisexual lineages usually comprise only females and utilize co-occurring males of a related sexual species to reproduce via gynogenesis or hybridogenesis. Here, we examine patterns of microsate...

Although conventional breeding programs in fish parallel those in chicken, unconventional techniques not available in chicken breeding, such as intersmecific hybridization (Schwartz, 1981), ploidy manipulation and gynogenesis (Thorgaard and Allen, 1987), are used in breeding of fishes. Within the last five years, another unconventional means of genetic manipulation, gene transfer, has become av...