Histological characterization of cuticular depositions throughout the molting cycle of the black tiger shrimp (Penaeus monodon)

Abstract

The aim of this study was to investigate changes of cuticular deposition throughout the molting cycle of the black tiger shrimp (Penaeus monodon). The molting stages were first determined using physical criteria. Then the deposition of collagen fibers, carbohydrate, lipid and calcium salt in the cuticle were examined histologically throughout the molting cycle. The results show that the mature cuticle of the intermolt stageshrimp is composed of four sub-layers from exterior to interior including an epicuticle, an exocuticle, an endocuticle, and a membranous layer. The differences of cuticular depositions reflect the different functions of each cuticular sub-layer. We also investigated the changes of these depositions that were related to the molting cycle. We found that the dynamic process of cuticular degradation and regeneration occurred constantly throughout the molting cycle. During the premolt period, the new epicuticle and exocuticle (preecdysial cuticle) were synthesized on the inside of the old ones. After exuviations (post-ecdysis), the syntheses of the endocuticle and membranous layer of the new cuticle progressed chronologically. When the synthesis of the membranous layer is complete, the shrimps then enter the intermolt stage. At the end of this paper, we also summarize the histological criteria to use for determining the stage of the molt in the black tiger shrimp.

Keywords

• cuticular sub-layers
• molting stages
• Penaeus monodon