Impact of the insect growth regulator diflubenzuron on biochemical composition of cuticle of the shrimp Penaeus kerathurus

Diflubenzuron (Dimilin 25WP) is an insecticide of the class of benzoylphenylurea (BPUs) and is widely used in the control of insect pest in agriculture and forestry. Typically, these chemistries prevent the moulting process by inhibiting chitin formation and thereby causing abnormal cuticular deposition and abortive moulting in insect and crustacean species. In a previous study, we have shown that diflubenzuron could cause a modification in the lamellar ultrastructural, particularly in the membranous layers, in the non-target organism, the caramote prawn or triple-grooved shrimp Penaeus kerathurus (Forskal, 1775) (Decapoda, Peneidae). Therefore, the aim of this study was to evaluate under laboratory conditions the potential side-effects of diflubenzuron on the biochemical composition of the cuticle of treated P. kerathurus. Diflubenzuron was added to the rearing seawater at a final concentration of 1 microg/L) and newly-ecdysed adult shrimps were exposed for 10 days, i.e. until stage C during the molting cycle. The most typical treatment symptoms were a significantly reduced thickness of both the principal and membranous layers, and reduced amounts of chitin in the cuticle. These symptoms help in explaining the structural alterations observed in treated cuticles, and confirm the primary mode of action of diflubenzuron to inhibit chitin biosynthesis.