| Summary: | The present chapter aims at describing the main biological characteristics of two oyster species, both important for their commercial values. Oyster spermatozoa belong to the "aquasperm" according to ultra-structural data: they possess an acrosome and four mitochondria. The sperm flagellum is devoid of progressive motility eitheir in the gonads or at spawning in sea water. In both cases, flagellar motility (% of moving cells) appears slowly in a time dependent manner in natural sea water (5 to 15 min). This ability to acquire potentiality for motility (maturation process) can be accelerated by sperm incubation with drugs like serotonine, theophilline, caffeine or dibutyryl-cAMP, which rapidly initiate progressive movement of live sperm. All drugs are effective in a time dependent manner and especially caffeine and theophilline are shown to act in a concentration dependent manner. These drugs allow forwardly directed translation for the majority of sperm cells. Furtheremore, spermatozoa induced to such efficient swimming behavior exhibit fertilizing performances of high levelDuring hatchery practices, oyster sperm are frequently collected by scarification of the male gonad alternatively, ejaculation can be induced by various methods. According to our results, injection of compounds such as serotonine (1 to 10mM) in the male gonad leads to release of sperm in sea water. By dilution into regular sea water, live oyster spermatozoa obtained by scarification show initially mostly erratic movements with poor efficiency for forward translation and initiate efficient flagellar motility after several minutes.Motility of black-lip pearl oyster spermatozoa appears gradually when spermatozoa are transferred into alkaline sea water. This motility-activating effect is reversed when pH is shifted back to acidic values; as in normal sea water, activity of sperm (% motile cells) increases gradually after alkaline pH activation and lasts for several minutes. The characteristics of these fully motile spermatozoa are described in ...
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