The Study of Sperm Penetration through the Vitelline Envelope of Penaeus monodon Egg
This study aims to elucidate the process and mechanism of sperm penetration through eggs of Penaeus monodon. Sperm penetration of the vitelline envelopes (VEs) of P. monodon eggs were observed with the scanning electron microscope. The characteristics of sperm proteases in the sperm extracts from seminal receptacles of females were analysized.
In P. monodon, mating and sperm transfer to the thelycum of female occur soon after maturity moult. Females store the sperm in the seminal receptacles. At spawning, they release stored sperm and eggs simultaneously into the water column. The outermost investment of a newly spawned egg is the VE. Sperm bind to the VE via the tip of their anterior spike. They rapidly undergo the acrosome reaction, which composes of depolymerization of the spike and exocytosis of the acrosome vesicle, pass through the VE and become bound to the egg oolemma.
The isolated sperm suspended in artificial seawater were disrupted by sonication on ice. The supernatants after microcentrifuged were collected as sperm extracts. Sperm extracts were analyzed by gelatin SDS-PAGE. Sperm extract from sperm isolated from seminal receptacles of females showed clear bands of protease activity, whereas sperm extract from vas deferens and spermatophore of males did not. This results indicated that sperm of P. monodon do proceed capacitation in the seminal receptacles, and obtain sperm protease activity after capacitation. Using fluorescent peptidyl-MCA as sperm protease substrates, high trypsin-like and aminopeptidase-like activities were observed in sperm extracts. The sperm protease activity was inhibited by trypsin inhibitors aprotinin, p-aminobenzamidine (PAB), soybean trypsin inhibitor (SBTI), N-£\-p-tosyl-L-lysinechloromethyl ketone (TLCK); but was not inhibited by chymotrypsin inhibitor N-tosyl-L-phenylalaninechloromethyl ketone (TPCK) and metalloprotease inhibitor 1,10-phenanthroline (1,10-P). The results indicated that sperm undergo the acrosome reaction and release sperm proteases including trypsin-like protease, which has been implicated in facilitating sperm passage through vitelline envelope.
Sperm proteases were highly active in the weak base environment, exhibiting maximum activity at pH 8.0. The protease activities were enhanced by addition of calcium chloride and magnesium chloride in the incubation medium.
Advisor:Houng-Yung Chen; Jin-Hua Cheng; Tzyy-Ing Chen
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:penetration egg penaeus monodon vitelline envelop sperm
Date of Publication:08/22/2001