Gene traffic mediated by transposable elements shaped the dynamic evolution of ancient sex chromosomes of varanid lizard.

Lizards usually exhibit frequent turnovers and a much greater diversity of sex determination mechanisms compared to birds and mammals, with the conserved ZW sex chromosomes of anguimorph lizards originating over 115 million years ago a seeming exception. We previously discovered in an anguimorph lizard Varanus acanthurus (Vac) whose entire chrW, but not chrZ is homologous to part of the chr2 by cytogenetic mapping, suggesting its complex history of sex chromosome evolution yet to be elucidated. To address this, we assemble a chromosome-level genome, and provide evidence that the Vac sex chromosome pair has undergone at least two times of recombination loss, producing a pattern of evolutionary strata like that of birds and mammals.

Repeatome Dynamics and Sex Chromosome Differentiation in the XY and XYY Systems of the Fish (Teleostei; Characiformes).

The wolf fish is a Neotropical species characterized by remarkable karyotypic diversity, including seven karyomorphs (KarA-G) with distinct sex chromosome systems. This study investigated the homologous XY (KarF) and XYY (KarG) sex chromosome systems present in this species by integrating cytogenetics and genomics to examine sex chromosomes' composition through characterization of repeatome (satellite DNA and transposable elements) and sex-linked markers. Our analysis indicated that both karyomorphs are little differentiated in their sex chromosomes content revealed by satDNA mapping and putative sex-linked markers.

Multigenerational effects of metals accumulate over three generations in the amphibian-killing fungus (Batrachochytrium dendrobatidis).

Exposure experiments within a single generation assess organisms' sensitivity to pollutants but don't reveal long-term effects over multiple generations. We studied the multigenerational effects (MGEs) of copper (Cu), zinc (Zn), and their combination (Cu+Zn) on the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) over three generations. Our goal was to determine if Bd's sensitivity to metals changes with continuous exposure, which should affect its long-term performance at metal-polluted sites.

Evolution of ZW Sex Chromosomes in Snakes (Reptilia, Colubridae): New Insights from a Molecular Cytogenetic Perspective.

Snakes are cytogenetically dynamic, characterized by largely conserved diploid chromosome numbers although displaying varied variable evolutionary stages of their sex chromosomes. This study examined four snakes, with a special focus on the genus , to provide evolutionary insights into the evolution of ZW sex chromosomes. We performed an extensive karyotype characterization using conventional and molecular cytogenetic approaches, described for the first time the karyotype of and revisited the karyotype descriptions of , , and .

Independent evolution of satellite DNA sequences in homologous sex chromosomes of Neotropical armored catfish (Harttia).

The Neotropical armored catfish Harttia is a valuable model for studying sex chromosome evolution, featuring two independently evolved male-heterogametic systems. This study examined satellitomes-sets of satellite DNAs-from four Amazonian species: H. duriventris (XXY), H.

The role of unbalanced segmental duplication in sex chromosome evolution in Australian ridge-tailed goannas.

Varanids are known for conserved sex chromosomes, but there are differences in the size of the W chromosome but not in morphology among species representing varying stages of sex chromosome evolution. We tested for homology of the ZW sex chromosome system with size differences in varanids among four species from two lineages in Australia, the Odatria and the Gouldii. We found that while DNA sequences of the sex chromosomes are conserved in the species we tested, we also identified a homologous region on an enlarged autosomal microchromosome that shares sequences with the W chromosome in some isolated populations of V.

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.

Multiple Transitions between Y Chromosome and Autosome in Tago's Brown Frog Species Complex.

Sex chromosome turnover is the transition between sex chromosomes and autosomes. Although many cases have been reported in poikilothermic vertebrates, their evolutionary causes and genetic mechanisms remain unclear. In this study, we report multiple transitions between the Y chromosome and autosome in the Japanese Tago's brown frog complex.

Using a Handful of Transcriptomes to Detect Sex-Linked Markers and Develop Molecular Sexing Assays in a Species with Homomorphic Sex Chromosomes.

To understand the biology of a species, it is often crucial to be able to differentiate males and females. However, many species lack easily identifiable sexually dimorphic traits. In those that possess sex chromosomes, molecular sexing offers a good alternative, and molecular sexing assays can be developed through the comparison of male and female genomic sequences.

Genomic Basis of Freshwater Adaptation in the Palaemonid Prawn Genus Macrobrachium: Convergent Evolution Following Multiple Independent Colonization Events.

Adaptation to different salinity environments can enhance morphological and genomic divergence between related aquatic taxa. Species of prawns in the genus Macrobrachium naturally inhabit different osmotic niches and possess distinctive lifecycle traits associated with salinity tolerance. This study was conducted to investigate the patterns of adaptive genomic divergence during freshwater colonization in 34 Macrobrachium species collected from four continents; Australia, Asia, North and South America.

Preserving Pure Siamese Crocodile Populations: A Comprehensive Approach Using Multi-Genetic Tools.

Hybrids between the critically endangered Siamese crocodile () and least-concern saltwater crocodile () in captive populations represent a serious challenge for conservation and reintroduction programs due to the impact of anthropogenic activities. A previous study used microsatellite and mitochondrial DNA data to establish the criteria for identifying species and their hybrids; however, the results may have been influenced by biased allelic frequencies and genetic drift within the examined population. To overcome these limitations and identify the true signals of selection, alternative DNA markers and a diverse set of populations should be employed.

Following the Pathway of W Chromosome Differentiation in (Teleostei: Characiformes).

In this work, we trace the dynamics of satellite DNAs (SatDNAs) accumulation and elimination along the pathway of W chromosome differentiation using the well-known fish model. stands out due to a conserved ZZ/ZW sex chromosome system present in all examined species. While the Z chromosome is conserved in all species, the W chromosome is invariably smaller and exhibits differences in size and morphology.

Fixed Allele Differences Associated With the Centromere Reveal Chromosome Morphology and Rearrangements in a Reptile (Varanus acanthurus BOULENGER).

Chromosome rearrangements are often implicated with genomic divergence and are proposed to be associated with species evolution. Rearrangements alter the genomic structure and interfere with homologous recombination by isolating a portion of the genome. Integration of multiplatform next-generation DNA sequencing technologies has enabled putative identification of chromosome rearrangements in many taxa; however, integrating these data sets with cytogenetics is still uncommon beyond model genetic organisms.

Cytogenetics Meets Genomics: Cytotaxonomy and Genomic Relationships among Color Variants of the Asian Arowana .

(Osteoglossiformes, Teleostei) represents one of the most valued ornamental fishes, yet it is critically endangered due to overexploitation and habitat destruction. This species encompasses three major color groups that naturally occur in allopatric populations, but the evolutionary and taxonomic relationships of color varieties remain uncertain. Here, we utilized a range of molecular cytogenetic techniques to characterize the karyotypes of five color phenotypes, which correspond to naturally occurring variants: the red ones (Super Red); the golden ones (Golden Crossback and Highback Golden); the green ones (Asian Green and Yellow Tail Silver).

Widespread chromosomal rearrangements preceded genetic divergence in a monitor lizard, Varanus acanthurus (Varanidae).

Chromosomal rearrangements are often associated with local adaptation and speciation because they suppress recombination, and as a result, rearrangements have been implicated in disrupting gene flow. Although there is strong evidence to suggest that chromosome rearrangements are a factor in genetic isolation of divergent populations, the underlying mechanism remains elusive. Here, we applied an integrative cytogenetics and genomics approach testing whether chromosomal rearrangements are the initial process, or a consequence, of population divergence in the dwarf goanna, Varanus acanthurus.

Sex-linked markers in an Australian frog Platyplectrum ornatum (Limnodynastidae) with a small genome and homomorphic sex chromosomes.

Amphibians have highly diverse sex-determining modes leading to a notable interest in vertebrate sex determination and sex chromosome evolution. The identification of sex-determining systems in amphibians, however, is often difficult as a vast majority consist of homomorphic sex chromosomes making them hard to distinguish. In this study, we used Diversity Array Technology sequencing (DArTseq) to identify the sex-determining system in the ornate burrowing frog from Australia, Platyplectrum ornatum.

Diversity of reptile sex chromosome evolution revealed by cytogenetic and linked-read sequencing.

Reptile sex determination is attracting much attention because the great diversity of sex-determination and dosage compensation mechanisms permits us to approach fundamental questions about mechanisms of sex chromosome turnover. Recent studies have made significant progress in better understanding diversity and conservation of reptile sex chromosomes, with however no reptile master sex determination genes identified. Here we describe an integrated genomics and cytogenetics pipeline, combining probes generated from the microdissected sex chromosomes with transcriptome and genome sequencing to explore the sex chromosome diversity in non-model Australian reptiles.

Highly rapid and diverse sex chromosome evolution in the Odorrana frog species complex.

Sex chromosomes in poikilothermal vertebrates are characterized by rapid and diverse evolution at the species or population level. Our previous study revealed that the Taiwanese frog Odorrana swinhoana (2n = 26) has a unique system of multiple sex chromosomes created by three sequential translocations among chromosomes 1, 3, and 7. To reveal the evolutionary history of sex chromosomes in the Odorrana species complex, we first identified the original, homomorphic sex chromosomes, prior to the occurrence of translocations, in the ancestral-type population of O.