Possible effects of a synthetic juvenoid hormone (Pyriproxyfen) on larval development, metamorphosis and survival of a crustacean octopod, Macrobrachium rosenbergii, was studied. Although Pyriproxyfen is well known as an effective pest control product, our knowledge about its effects on crustacean metamorphosis, especially on larval stages is yet little. Macrobrachium rosenbergii is a suitable invertebrate species in the neurobiological and endocrinological researches. The species has II larval stages with obvious morphological features for every stage. In this study, larvae of the species were treated with 0.01, 0.05 and 0.1 ppm of Pyriproxyfen against a group of control for which xylene was used. In the first day of exposure to the Pyriproxyfen, all larvae were in the 1st larval stage. We studied the larval stages in samples obtained in different days and percentage of survival in the end of metamorphosis for treatment and control groups. The results showed that all concentrations of Pyriproxyfen significantly caused a delayed larval development and metamorphosis. Furthermore, the post larval survival rates of all treatment groups were less than control. These results suggest that synthetic juvenoid hormone retards the larval morphological development in Macrobrachium rosenbergii, and decreases the survival of the species
