EFFECT OF METHYL FARNESOATE ON LATE LARVAL DEVELOPMENT AND METAMORPHOSIS IN THE PRAWN MACROBRACHIUM-ROSENBERGII (DECAPODA, PALAEMONIDAE) - A JUVENOID-LIKE EFFECT

Methyl farnesoate (MF), the unepoxidated form of insect juvenile hormo ne III, was detected in larvae of the freshwater prawn Macrobrachium r osenbergii, which metamorphose to post-larvae following Ii larval stag es. The possible role of MF as a morphogen was studied by administerin g the compound to M. rosenbergii larvae via an Artemia vector. Higher MF levels caused earlier retardation of late larval growth, and the hi ghest dose retarded larval development. Furthermore, MF significantly affected the patterns of metamorphosis and the appearance of intermedi ate individuals exhibiting both larval and post-larval morphology and behavior. Three intermediate types were defined, two of which were fou nd only at the MF-treated groups and one that was exclusive to the hig her dose treatments. The relative abundance of intermediate specimens increased from 2% in the control to 32% in the high MF concentration, which suggests that MF has a juvenoid-like effect in this decapod crus tacean.