Survival of Polyploid hybrid salamander embryos

Abstract

BackgroundAnimals with polyploid, hybrid nuclei offer a challenge for models of gene expression and regulation during embryogenesis. To understand how such organisms proceed through development, we examined the timing and prevalence of mortality among embryos of unisexual salamanders in the genus Ambystoma.ResultsOur regional field surveys suggested that heightened rates of embryo mortality among unisexual salamanders begin in the earliest stages of embryogenesis. Although we expected elevated mortality after zygotic genome activation in the blastula stage, this is not what we found among embryos which we reared in the laboratory. Once embryos entered the first cleavage stage, we found no difference in mortality rates between unisexual salamanders and their bisexual hosts. Our results are consistent with previous studies showing high rates of unisexual mortality, but counter to reports that heightened embryo mortality continues throughout embryo development.ConclusionsPossible causes of embryonic mortality in early embryogenesis suggested by our results include abnormal maternal loading of RNA during meiosis and barriers to insemination. The surprising survival rates of embryos post-cleavage invites further study of how genes are regulated during development in such polyploid hybrid organisms.

Origin of scarlet gynogenetic triploid Carassius fish: Implications for conservation of the sexual–gynogenetic complex

“…Similar increases in ploidy levels resulting from sperm nuclear incorporation have been reported in several gynogenetic vertebrate species, such as Poecilia fish, Amazon molly, and unisexual salamander in the genus Ambystoma [ 44 ]. Although the sex and reproductive mode of these species remain poorly characterized, the tetraploid Ambyostoma unisexuals have been shown to have a higher rate of developmental defects and greater larval mortality than triploids, probably due to the misconfiguration in parthenogenetic egg development by ploidy elevation [ 44 – 46 ]. The occurrence of both male and female tetraploid Carassius exhibiting different reproductive modes could be a unique characteristic among asexual vertebrates.…”