Percichthyids as a novel model for studying sex chromosome
turnover
Sex-determining mechanisms are extremely diverse and may vary even in
closely-related species or among populations of the same species (Kijas
et al., 2018; Lubieniecki et al., 2015; Rodrigues, Merilä, Patrelle, &
Perrin, 2014). In species with genotypic sex determination, an ancestral
sex-determining locus can be replaced by another locus on the same or a
different chromosome, resulting in chromosome turnover. Transitions to a
different chromosome are more likely when sex chromosomes exhibit little
differentiation, so that WW or YY genotypes are less likely to be lethal
(Bachtrog et al., 2014). Therefore, species with homomorphic chromosomes
and intraspecific variation of sex-determining loci provide a window
into sex chromosome evolution in real time. Macquarie perch, with an
order of magnitude fewer sex-linked loci than its sister-species golden
perch, appears to have more recently-evolved sex chromosomes. Its
XY-gametologous locus, putatively sex-determining in at least the two
populations used in assay development, was less correlated with
phenotypic sex in other populations and not sex-linked in other
percichthyids. Whereas population-specific variation in genetic factors
determining phenotypic sex has been observed in other fish species
(Faggion, Vandeputte, Chatain, Gagnaire, & Allal, 2019; Ferraresso et
al., 2021), it is also possible that genotypic sex determination in
different Macquarie perch populations is variably influenced by
environmental variation (Hill, Burridge, Ezaz, & Wapstra, 2018). In
contrast to sex chromosomes of perches, heteromorphic chromosomes of the
Murray cod (Shams et al., 2019) must be the oldest among the three
percichthyids with sequenced genomes. The interspecific variation in
candidate sex-determining mechanisms makes Percichthyidae a good system
for studying sex chromosome turnover and dosage compensation.
Comparative studies that demonstrate sex chromosome turnover within the
same genus or families are still relatively rare (e.g. Gambusia(Kottler et al., 2020), Oreochromis (Tao et al., 2021),Oryzias (Tanaka, Takehana, Naruse, Hamaguchi, & Sakaizumi,
2007), Poeciliidae (Darolti et al., 2019; Schultheis, Böhne, Schartl,
Volff, & Galiana-Arnoux, 2009), Gasterosteidae (Ross, Urton, Boland,
Shapiro, & Peichel, 2009)).