Pyriproxyfen, a juvenoid hormone analog, does not induce male production in parthenogenetic lineages of Eucypris virens (Crustacea: Ostracoda)

Analogs of juvenoid hormones are increasingly recommended for controlling insect pests in agriculture. One of these analogs, pyriproxyfen, was found to be very potent in inducing male production in Daphnia under laboratory conditions, even after acute exposure. Other studies also demonstrated a major role of juvenoid hormones for the sex determination in arthropods that have sex chromosomes. We exposed parthenogenetic lineages of the freshwater ostracod Eucypris virens to a wide range of pyriproxyfen concentrations, and compared mortality and fecundity between treated and control animals. Animals exposed to the highest concentrations of pyriproxyfen (3-30 nM) experienced a higher mortality than control animals, but no treatment effects were found on the production rates of eggs and hatchlings. Also, hatchlings that emerged from eggs deposited by treated individuals did not suffer from an increased mortality rate. No males were found among the 91 hatchlings that could be grown to adulthood. These results suggest that previous observations of a reduced population growth of ostracods in treated field crops might not be due to an alteration of the sex ratio, but rather to an increased mortality of the exposed females.