A simple technique to stage the moult of Penaeus monodon

Abstract

Growth in crustaceans and other arthropods is interrupted by cyclical moults, in which the old cuticle or exoskeleton is shed, and in the intervening growth phases the soft tissue swells and a new elastic cuticle gradually thickens and hardens. Marine prawns, Penaeus monodon, from a commercial farm in northern Queensland, Australia, were studied alive to assess their growth and moulting stages. The median part of the setae of inner uropods was examined by light microscopy. A finely graded classification of five stages and substages of postmoult, stage A consisting of substages A1 and A2, and stage B (1-16 hours); intermoult, stage C (1 day); premoult, stage D consisting of substages D1, D2 and D3/D4 (2-12 days) and ecdysis, stage E (about one minute) are described and illustrated. Ecdysis took place at night. Rapid and repetitive moult staging in individual prawns can be carried out without sacrificing the prawns.