A new type of sex determinant found in a woodlouse

SemIDEEV
 23/01/2026
 12:00:00
 Jean Peccoud, Laboratoire Ecologie et Biologie des Interactions, Université de Poitiers
 IDEEV - Salle Rosalind Franklin

In animals, sex can be determined by environmental or chromosomal factors, or by maternally inherited microorganisms that feminize their hosts, thereby enhancing their transmission rates. These so-called feminizing symbionts comprise Wolbachia bacteria infecting woodlice (terrestrial isopods). In these species, females infected by feminizing bacteria carry male sex chromosomes. The transmission rate of the symbiont therefore governs sex ratios.

In the woodlouse Armadillidium arcangelii however, strong sex-ratio biases observed in certain populations are not due to a known microbe. Females producing biased sexe-ratios are not only identical to males in their genome, they are also indistinguishable from “regular” females in their microbiome. Investigating sex determination in these populations allowed us to uncovered a new type of heritable sex determinant.