A bisexually reproducing all-triploid vertebrate

Abstract

Green toads are common in the Palaearctic region, where they have differentiated into several taxa. The toads exist with variable amounts of ploidy, similar to other anuran species or reptiles. In vertebrate biology, the very rare occurrence of triploidy is coupled with infertility or unisexuality, or requires the coexistence of individuals of different ploidy in a reproductive community. The reproduction of naturally occurring triploids has been reported to occur only through parthenogenesis, gynogenesis or hybridogenesis. The bisexual reproduction of pure triploids has been considered to be impossible because of the problem of equally distributing three chromosome sets in meiosis. Here we report geographically isolated populations of green toads (Bufo viridis complex) that are all-triploid and reproduce bisexually.

High male incidence and evolutionary implications of triploid form in northeast Asia Carassius auratus complex

“…Practically, we have synthesized a novel nucleo-cytoplasmic hybrid clone through sexual reproduction mating between different clones in the triploid gibel carp, and rapidly amplified the population with more than several billions of clonal individuals by seven successive generations of unisexual gynogenesis (Wang et al, 2011). Previously, all-triploid populations that reproduce bisexually were also reported at certain habitats in two species of triploid amphibians, such as green toads (Bufo viridis) (Stöck et al, 2002) and water frogs (Pelophylax esculentus) (Christiansen and Reyer, 2009). Therefore, these interesting findings in vertebrates seem to imply that a similar mechanism might operate in the triploid vertebrates including Carassius auratus gibelio.…”

Parental genomes mix in mule and human cell nuclei

“…Examples are the water frog Rana esculenta (e.g., Spolsky and Uzzell 1984;Guerrini et al 1997) and the fish Poeciliopsis monacha x lucida (Quattro et al 1991). In a triploid population of the toad Bufo viridis, in males, one haploid genome is eliminated before the onset of meiosis (Stöck et al 2002).…”

Simultaneous Mendelian and clonal genome transmission in a sexually reproducing, all-triploid vertebrate

“…In this context, Batura toads (Bufo baturae) are exceptional in being sexually reproducing triploids [25]. This species of hybrid origin inhabits the high mountains of northern Pakistan (greater than 1500 m a.s.l.).…”

“…In contrast, ova are diploid (2n ¼ 22) with one NORþ and one NOR2 sets. Immature oocytes exhibit 22 lampbrush chromosome bivalents [25].…”

“…This species of hybrid origin inhabits the high mountains of northern Pakistan (greater than 1500 m a.s.l.). Its genome (3n ¼ 33; [25,26]) is composed of two chromosome sets carrying a nucleolus-organizing region (NORþ) on chromosome 6, and another set without such a region (NOR2; figure 2). Males only produce haploid NORþ sperm, suggesting elimination of the NOR2 set (11 chromosomes) before the onset of meiosis.…”