ZO sex-determination system
Biological system in certain moths
From Wikipedia, the free encyclopedia
The ZO sex-determination system is a system that determines the sex of offspring in caddisflies and several moths. In those species, there is one sex chromosome, Z. Males have two Z chromosomes, whereas females have one Z. Males are ZZ, while females are ZO.
[1][2][3] The ancestor of Lepidoptera and Trichoptera had ZO sex determination, which became a ZW sex-determination system in the largest clade, Ditrysia, as well as in Tischerioidea.
Some of the ZW species later reverted to the ZO system.[1]
In 2025 coleoid cephalopods (octopuses, squids, and cuttlefishes) were revealed to have a ZO sex chromosome system[4].
