Oxidase Activity Associated with the Elevation of the Penaeoid Shrimp Hatching Envelope

Abstract

When penaeoid shrimp spawn into seawater, the ova elevate a hatching envelope (HE) within 30-50 min. By 60 min after spawning, the bilayered HE is completely formed. In other animal systems, peroxidatic enzymes are responsible for the hardening of the extra-embryonic coat. In this study, observations are made consistent with the involvement of an oxidase in the assembly of the shrimp HE. As observed by electron microscopy, eggs of Sicyonia ingentis and Trachypenaeus similis spawned in seawaters containing peroxidase inhibitors had abnormally assembled HEs compared to control eggs in seawater. Dihydrotetramethylrosamine, an oxidase-sensitive fluorescent dye, supravitally stained the cortex of S. ingentis eggs at the time of initial HE formation. The HE fluoresced from elevation (40-50 min postspawn in S. ingentis) until 60-70 min postspawn. By first cleavage (90-120 min postspawn), HE staining was no longer visible, although staining persisted in the egg cortex. In eggs treated with the peroxidase inhibitors 3-amino-1,2,4-triazole or sodium sulfite, the egg cortex fluoresced, but no fluorescence appeared in the HE before, during, or after its elevation.