protandric

Protandric refers to a pattern of sequential hermaphroditism in which an organism begins life as male and later becomes female. The term is derived from Greek roots meaning first man, reflecting the shift from male to female function as individuals mature. Protandry is contrasted with protogyny, where the sequence is female to male.

Occurrence and drivers vary by lineage but are most commonly documented in marine fishes. The best-known protandrous group is the clownfishes (Amphiprioninae), where social structure and size influence sex role: the dominant individual becomes female, a subordinate male can assume breeding status, and a removal of the female can trigger a male to change sex. Protandry has also been observed in certain invertebrates, including some mollusks and crustaceans, though its prevalence is taxon-specific.

Physiologically, sex change involves dramatic gonadal remodeling—from testes to ovaries—and accompanying hormonal shifts that regulate gamete development and secondary sexual traits. In fishes, hormones such as estrogens and androgens change in response to social and environmental cues, enabling the transition.

Adaptive explanations emphasize maximizing reproductive success. Because female fecundity often increases with body size, switching to female later in life allows individuals to invest early as males—securing mating opportunities—while later leveraging larger size for greater egg production.

See also: sequential hermaphroditism, gonadal development, fish reproduction.