Morphogenesis of the eyestalk and expression of moult-inhibiting hormone during embryonic development of the freshwater prawn, Macrobrachium rosenbergii (Decapoda, Palaemonidae)

The morphogenesis of the compound eyes and eyestalks during embryonic development of Macrobrachium rosenbergii was characterized by using histological methods. The expression of moult-inhibiting hormone (MIH) at different stages of embryonic development was determined by the reverse transcription polymerase chain reaction (RT-PCR). Histological studies showed that compound eye pigment began to assemble and the eyestalk Anlage appeared during the protozoea stage. During the zoea stage, the eyestalk appeared and the structure of the compound eye was similar to that of the adult. RT-PCR results showed that MIH was expressed during both the late protozoea and early zoea stages of development. However, MIH was not expressed in the fertilized egg until the early protozoea stages or during the late zoea stage. MIH expression was detected only after the appearance of the eyestalk. The expression of MIH correlates closely with the morphogenesis of the compound eye and eyestalk. The absence of MIH expression during the zoea stage demonstrates that it regulates the synthesis of ecdysteroids in preparation for the first moult after hatching.