A MORPHOLOGICAL EXAMINATION OF SPERM-EGG INTERACTION IN THE FRESHWATER PRAWN,MACROBRACHIUM ROSENBERGII

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Abstract
Eggs, covered by a bilayered investment composed of a 0.5 .mu.m protein outer layer and a 2.5 .mu.m mucopolysaccharide inner layer, are spawned through an externally held spermatophore following a female''s ovigerous molt and mating. Mature sperm resemble everted umbrellas and consist of a cupped base with a single spike projecting from the covex surface. These sperm (< 5/egg) attach base-first with the spike oriented perpendicularly to the investment. Within 15 s, the spike of the sperm bends at the base and contacts the investment. The spike penetrates the investment, the base is inverted and fertilization occurs within 2 min. The spike remains briefly as a central core in the fertilization cone. The meiotic division of the egg resumes at this stage. First karyokinesis is completed .apprx. 6 h post fertilization, but cytokinesis is suppressed until following the 2nd karyokinesis at 8 hours postfertilization. First 2nd cytokinesis are simultaneous; at 9 h the egg cleaves to the 4 cell stage.