Sex chromosome evolution in frogs—helpful insights from chromosome painting in the genus Engystomops

Abstract

The differentiation of sex chromosomes is thought to be interrupted by relatively frequent sex chromosome turnover and/or occasional recombination between sex chromosomes (fountain-of-youth model) in some vertebrate groups as fishes, amphibians, and lizards. As a result, we observe the prevalence of homomorphic sex chromosomes in these groups. Here, we provide evidence for the loss of sex chromosome heteromorphism in the Amazonian frogs of the genus Engystomops, which harbors an intriguing history of sex chromosome evolution. In this species complex composed of two named species, two confirmed unnamed species, and up to three unconfirmed species, highly divergent karyotypes are present, and heteromorphic X and Y chromosomes were previously found in two species. We describe the karyotype of a lineage estimated to be the sister of all remaining Amazonian Engystomops (named Engystomops sp.) and perform chromosome painting techniques using one probe for the Y chromosome and one probe for the non-centromeric heterochromatic bands of the X chromosome of E. freibergi to compare three Engystomops karyotypes. The Y probe detected the Y chromosomes of E. freibergi and E. petersi and one homolog of chromosome pair 11 of Engystomops sp., suggesting their common evolutionary origin. The X probe showed no interspecific hybridization, revealing that X chromosome heterochromatin is strongly divergent among the studied species. In the light of the phylogenetic relationships, our data suggest that sex chromosome heteromorphism may have occurred early in the evolution of the Amazonian Engystomops and have been lost in two unnamed but confirmed candidate species. Associate editor Ben Evans

Evolutionary breakpoint regions and chromosomal remodeling in Harttia (Siluriformes: Loricariidae) species diversification

“…Thus, the generation of probes from whole chromosomes or specific chromosomal regions obtained primarily by microdissection can be established ( Guan et al, 1994 , 1996 ). Chromosome painting can be used to identify homeologous segments and rearrangements during karyotype evolution ( Yang et al, 2000 ; Ventura et al, 2009 ; Schemberger et al, 2011 ; Deng et al, 2013 ; Gokhman et al, 2019 ; Targueta et al, 2021 ). In teleosts, where banding patterns are not easily induced, a series of chromosomal rearrangements can be underestimated ( Sharma et al, 2002 ).…”

Larval morphology of Amazonia foam‐nesting frogs of the genus Engystomops (Anura: Leptodactylidae: Leiuperinae)

“…The functional and ecological significance of E. petersi glands has not been reported. It is important to know the tadpole of E. freibergi, the sister species of E. petersi, as well as the several populations of E. petersi that have shown consistently differences in calls, cytogenetic, and molecular characters (Boul et al, 2007;Funk et al, 2012;Targueta et al, 2010Targueta et al, , 2021, to verify if these glands could have a wider distribution and represent a synapomorphy for the clade formed by these two species.…”

A Fish of Multiple Faces, Which Show Us Enigmatic and Incredible Phenomena in Nature: Biology and Cytogenetics of the Genus Carassius

“…Another way to distinguish maternal and paternal genome complements within hybrids is using FISH with whole chromosome painting probes. Individual chromosomes [ 99 ] or morphologically similar groups of chromosomes [ 58 ] can be separately dissected and used as a probe for in situ hybridization. The intensity of the fluorescent signal of painting probes can indicate evolutionary distance and distinguish parental subgenomes in biotypes that originate from interspecies hybridization [ 100 ].…”