Environmental sex determination

Definition

A sex-determination system in which sex is established by non-genetic environmental cues—such as temperature, photoperiod, nutrient availability, or chemical signals—experienced during a discrete sensitive period after fertilization, rather than by sex chromosomes at conception. Once established, sex is fixed and cannot be reversed, distinguishing this mechanism from sequential hermaphroditism.

Etymology

From environmental (surrounding conditions) + sex (biological reproductive role) + determination (establishment of state)

Example

In many reptiles and some invertebrates, incubation temperature dictates sex: cooler nests produce males, warmer nests females. Among insects, some parasitoid wasps exhibit environmental sex determination where host size or quality influences offspring sex ratios, with females typically developing from larger hosts.

Synonyms

• ESD

Related Terms

• genotypic sex determination
• sequential hermaphroditism
• temperature-dependent sex determination
• sex ratio
• phenotypic plasticity
• developmental plasticity

Usage Notes

Contrast with GSD (genotypic sex determination), where sex chromosomes fix sex at fertilization. Not interchangeable with sequential hermaphroditism, which allows sex change throughout life. In arthropods, ESD is less common than in reptiles but occurs in some crustaceans and parasitoids where maternal or environmental cues alter sex allocation strategies.