Groundbreaking Discovery: Earliest Sex Chromosomes in Vertebrates Uncovered in Sharks and Rays
Tokyo, Japan – July 30, 2025 – In a significant advancement for evolutionary biology and genetics, researchers at the University of Tokyo have announced the discovery of the oldest known sex chromosomes in vertebrates. Published today, their comprehensive study delves into the unique sex determination mechanisms of sharks and rays, shedding new light on the ancient origins of sex chromosomes.
The research, titled “Discovery of the Oldest Vertebrate Sex Chromosomes: Approaching the Unique Sex Determination of Sharks and Rays Through Genome Information,” was released by the University of Tokyo’s Advanced Research Institute for Science and Engineering (ARISE) at 01:00 JST. This landmark finding pushes back the timeline for the evolution of dedicated sex chromosomes, offering invaluable insights into the early development of sexual reproduction in the vertebrate lineage.
For decades, scientists have been actively researching the evolution of sex determination systems across different animal groups. While mammals, birds, and many other vertebrates possess well-defined sex chromosomes (like the XY system in humans and ZW system in birds), the evolutionary history and origin of these crucial genetic differentiators have remained a complex puzzle.
The University of Tokyo team, utilizing cutting-edge genomic analysis techniques, has meticulously investigated the genomes of various shark and ray species. Their findings reveal distinct chromosomal differences associated with sex in these cartilaginous fish, which are considered among the earliest diverging lineages of jawed vertebrates. Crucially, their analysis points to the presence of ancient sex-determining genes on specific chromosomes that have remained largely conserved over millions of years.
This discovery is particularly remarkable because it predates the previously recognized oldest sex chromosomes found in other vertebrate groups. The study suggests that the foundational mechanisms for sex chromosome differentiation were already in place in the common ancestor of cartilaginous fish, a lineage that branched off significantly earlier than the ancestors of bony fish, amphibians, reptiles, and mammals.
The implications of this research are far-reaching. By understanding the genetic architecture and evolutionary trajectory of these ancient sex chromosomes, scientists can gain a deeper appreciation for:
- The early evolution of sexual reproduction: This discovery provides critical clues about how sex determination mechanisms first arose and diversified in vertebrates.
- The conservation and divergence of sex chromosomes: It allows for comparative studies that can illuminate how sex chromosomes have been maintained or have undergone significant changes in different vertebrate lineages.
- The genetic basis of sex determination: The identification of specific genes involved in sex determination in sharks and rays can help unravel the fundamental genetic pathways that dictate maleness and femaleness.
- Evolutionary relationships: The patterns observed in these ancient sex chromosomes can also contribute to understanding the evolutionary history and relationships between different groups of vertebrates.
The researchers at the University of Tokyo have expressed excitement about the potential for further exploration. They anticipate that this breakthrough will pave the way for more in-depth studies on the genetic basis of sex determination in a wider range of ancient vertebrate species and will undoubtedly stimulate new avenues of research in evolutionary genetics and genomics.
This significant contribution from the University of Tokyo marks a pivotal moment in our understanding of vertebrate evolution and the fundamental processes that underpin life on Earth.
脊椎動物最古の性染色体の発見 ～ゲノム情報から迫るサメ・エイ類のユニークな性決定～
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東京大学 published ‘脊椎動物最古の性染色体の発見 ～ゲノム情報から迫るサメ・エイ類のユニークな性決定～’ at 2025-07-30 01:00. Please write a detailed article about this news in a polite tone with relevant information. Please reply in English with the article only.