Ecdysis Failure in Asian Horseshoe Crab Larvae of Tachypleus gigas under Laboratory Observation

Horseshoe crab has recently been categorized as a halal commodity which exposed them to unsustainable exploitation. As grouped among the arthropods, Asian horseshoe crab, Tachypleus gigas, rely on ecdysis to grow. The stage of ecdysis itself is the most crucial step in their life cycle and could cause death if it cannot be completed successfully. This study investigated the different types of ecdysis failure in the larval stage using Scanning Electron Microscope (SEM) technique. Samples of the moulted skeleton that were left behind after the ecdysis process were immediately collected and prepared for SEM. Three types of moulting failures were identified from the observation prosomatic failure, opishosomatic failure, and appendage failure. These failures were classified according to the position of the larvae body part where the exuviae were stuck at. Two out of three failures, prosomatic and opisthosomatic ecdysis failure would cause death instantly as the exuviae stuck at the vital organ, gills, and prevent it to function well in the breathing process. The micrograph obtained from the SEM study could be an important record for an evolutionary and growth study of this living fossil. It will also contribute to the understanding of the conservation effort for the species.