Preprint confirms ZZ/ZW sex-determination system in Pacific saury and maps sex-chromosome diversity in Beloniformes

A preprint posted to bioRxiv reports the genomic characterisation of the sex-determination system in Pacific saury (Cololabis saira), a commercially important fish in the order Beloniformes.

Using double-digest restriction-site-associated DNA sequencing (ddRAD-seq) and pooled whole-genome sequencing (Pool-seq), the authors identified numerous genetic markers that occur predominantly or exclusively in phenotypic females. Mapping of these markers indicated clustering consistent with a ZZ/ZW sex-determination system — one in which females carry two different sex chromosomes (ZW) and males carry two identical copies (ZZ), analogous to but distinct from the XY system found in humans.

The finding adds Pacific saury to a growing catalogue of teleost fish with characterised sex-determination mechanisms. Sex-determination in teleosts evolves rapidly and is unusually diverse; Beloniformes in particular show variation across species and the preprint discusses how the Pacific saury results fit within this broader picture. The authors also developed a DNA marker suitable for inferring genetic sex, which may have practical value for aquaculture and fisheries biology.

The study is relevant to researchers working on sex chromosome evolution, comparative genomics, and aquaculture genetics. This work is a preprint and has not yet undergone peer review.