Disruption of Sex-Linked Causes ZW Female-to-Male Sex Reversal in the Japanese Frog .

is an ancestral homologous gene of the male-determining in eutherian mammals and determines maleness in medaka fish. In the Japanese frog, , is located on the Z and W chromosomes. To assess the sex-determining function of in this frog, we investigated its expression in gonads during early tadpole development and conducted genome-editing experiments.

One-Step Leaping Evolution from an Autosomal Pair to the Heteromorphic Sex Chromosomes.

Background: Sex chromosomes evolve from an autosomal pair after the acquisition of a sex-determining gene. The primary sex chromosomes are homomorphic in both sexes and often undergo heteromorphism in either sex (XY in males or ZW in females) in association with chromosome rearrangements such as inversion, which creates a non-recombining region, called a stratum. Then, multiple strata may form by sequential inversions and extend the non-recombining region, where gene divergence accelerates, and degeneration of the Y or W chromosome progressively occurs.

Gradual chromosomal lagging drive programmed genome elimination in hemiclonal fishes from the genus Hypseleotris.

Most eukaryotes maintain the stability of their cellular genome sizes to ensure genome transmission to offspring through sexual reproduction. However, some alter their genome size by selectively eliminating parts or increasing ploidy at specific developmental stages. This phenomenon of genome elimination or whole genome duplication occurs in animal hybrids reproducing asexually.

Evidence for a metal disease refuge: The amphibian-killing fungus (Batrachochytrium dendrobatidis) is inhibited by environmentally-relevant concentrations of metals tolerated by amphibians.

The amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) has caused substantial declines in Bd-susceptible amphibian species worldwide. However, some populations of Bd-susceptible frogs have managed to survive at existing metal-polluted sites, giving rise to the hypothesis that frogs might persist in the presence of Bd if Bd is inhibited by metals at concentrations that frogs can tolerate. We tested this hypothesis by measuring the survival of Bd zoospores, the life stage that infects amphibians, and calculated the LC after exposure to environmentally-relevant elevated concentrations of copper (Cu), zinc (Zn), and their combination (Cu + Zn) in two repeated 4-day acute exposure runs.

Multiple karyotype differences between populations of the Hoplias malabaricus (Teleostei; Characiformes), a species complex in the gray area of the speciation process.

Neotropical fishes exhibit remarkable karyotype diversity, whose evolution is poorly understood. Here, we studied genetic differences in 60 individuals, from 11 localities of one species, the wolf fish Hoplias malabaricus, from populations that include six different "karyomorphs". These differ in Y-X chromosome differentiation, and, in several cases, by fusions with autosomes that have resulted in multiple sex chromosomes.