The Biological Bulletin, Vol 183, Issue 1 84-93, Copyright © 1992 by Marine Biological Laboratory

DEVELOPMENT AND REPRODUCTION

Assembly of the Hatching Envelope Around the Eggs of Trachypenaeus similis and Sicyonia ingentis in a Low Sodium Environment

J. W. Lynn, P. S. Glas and J. D. Green
Department of Zoology and Physiology, Louisiana State University, Baton Rouge, Louisiana 70803

The eggs of many penaeoidean shrimp undergo two dramatic morphological events when spawned into normal seawater (Lynn et al., 1991). Following the initial release of jelly precursor from crypts in the cortex of the egg, an extracellular envelope elevates and transforms into a substantial "hatching envelope" (HE) 30-40 min after spawning. The HE's of Sicyonia ingentis and Trachypenaeus similis eggs have distinct laminar morphologies and range from 90 to 110 nm thick. The HE elevates approximately 80 {mu}m from the egg in T. similis and 40 {mu}m from the egg in S. ingentis. Although eggs spawned into low Na+ artificial seawater (with choline chloride or Tris-HCl substituted for the NaCl) underwent normal release and formation of the jelly layer, the HE failed to develop normally. The HE retained a 100-nm thickness, but lacked the distinctive inner flocculent zone and dense outer covering. The HE collapsed to the egg surface, reducing the perivitelline space. Assembly of the HE resembles the formation of the sea urchin fertilization envelope and demonstrates a similar sensitivity to the lack of Na+ in the ambient environment.