Evolution of Sex Chromosomes in Cichlid Fishes Exposed

Researchers from the University of Maryland have published a new study on the evolution of sex chromosomes in cichlid fishes, revealing an extraordinary diversification of species in East Africa. The study, published in the journal Genome Biology and Evolution, investigates the sex chromosomes in six tribes of cichlid fishes and finds evidence of a high rate of sex chromosome turnover. The research suggests that ubiquitination may play a role in the evolution of sex chromosomes in some lineages.

Key Takeaways:

• The study found that cichlid fishes have undergone a high rate of sex chromosome turnover, with different species having different sex chromosome systems.
• The research identified six distinct sex chromosome systems in the studied tribes, including a ZW system in some species and an XY system in others.
• The phylogenetic distribution of these sex chromosome systems suggests a long period of polymorphism for some systems and a generally lower rate of sex chromosome turnover in certain lineages.
• The study found evidence of ubiquitination in the XY systems on LG3 and suggested a possible role for this process in the evolution of sex chromosomes.
• The researchers analyzed chromosome-scale genomes of male and female Pelmatotilapia mariae and mapped pooled sequencing reads for males and females of P. mariae and 12 additional species.
• The study involved the work of researchers from the University of Maryland, including Zexuan Zhao, Kristen A. Behrens, Michael R. Kidd, Alfred Maluwa, Avner Cnaani, Stephan Koblmuller, and Thomas D. Kocher.
• The research was published in the journal Genome Biology and Evolution and may be accessed through the journal's website.

Statistics:

• The study analyzed chromosome-scale genomes of male and female Pelmatotilapia mariae.
• The researchers mapped pooled sequencing reads for males and females of P. mariae and 12 additional species.
• The study identified six distinct sex chromosome systems in the studied tribes.
• The phylogenetic distribution of these sex chromosome systems suggests a long period of polymorphism for some systems.
• The study found evidence of ubiquitination in the XY systems on LG3.

Sources:

• [1] Zhao, Z., et al. (2025). Before the East African radiation: sex chromosome systems in basal haplotilapiine cichlids. Genome Biology and Evolution.