Developmental Capacity of Aneuploid Xenopus Species Hybrids

Diploid as well as triploid Xenopus interspecific hybrids generate aneuploid eggs because of the presence, at meiosis, of univalent chromosomes which are presumably distributed at random. Zygotes obtained from such eggs, fertilized by either normal or UV-irradiated sperm, were analysed for their developmental capacities. All monosomics die in the course of embryogenesis, whereby optimum capacities correspond closely with those observed in monosomic mammalian embryos, especially in mice. In contrast, hyperdiploid Xenopus are relatively viable: although many die exhibiting the'haploid syndrome'or various other abnormalities, 8% of them reach metamorphosis, and 1–2% become adults. Of the latter, the karyotype was established in 13 individuals. Among them, 8–16 supernumerary chromosomes were found to be present.