Demoy-Schneider, Marina, Schmitt, Nelly, Suquet, Marc, Labbé, Catherine, Boulais, Myrina, Prokopchuk, Galina, Cosson, Jacky, University of French Polynesia, UMR PFOM Department, Station Expérimental d'Argenton, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire de Physiologie et Génomique des Poissons (LPGP), Institut National de la Recherche Agronomique (INRA)-Structure Fédérative de Recherche en Biologie et Santé de Rennes ( Biosit : Biologie - Santé - Innovation Technologique ), UMR PFOM Department, Station Expérimentale d'Argenton, Faculty of Fisheries and Protection of Waters, Research Institute of Fish Culture and Hydrobiology, University of South Bohemia, CENAQUA (registration number CZ.1.05/2.1.00/01.0024. of Czech Republic) - Czech Agencies Projects: IAA 608030801, ME10015, QH82119, LC06073, CZ.1.05/2.1.00/01.0024, GACR P502/11/0090, GAJU 046/2010/Z, Brenda T. Erickson, and ProdInra, Archive Ouverte
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 details at the level of flagella: the wave amplitude and wave-length range 6 μm and 15 μm respectively, while the flagellar beat frequency is approximately 49 Hz. The velocity of sperm displacement is ranging 230 μm/sec. The swimming tracks are almost circular: the head trajectories describe portions of circles intercalated with small linear segments. Spermatozoa saved in natural sea water at 4°C retain potent motility for several days and can be subsequently activated by alkaline sea water.In case of the Pacific oyster, motility appears also to be under the control of acidic pH. This would explain how motility activation occurs when inactive sperm in seminal fluid (pH 5.5) comes in contact with sea water (pH 8.0) at shedding. Sperm movement is hasting for a long period (Pacific oyster: 20 to 72 h), suggesting spermatozoa could restore their energy stores. Therefore, the cessation of Pacific oyster sperm movement is unlikely caused by an insufficient concentation of ATPThis book chapter intends to describe in both species details of the present knowledge on the characteristics of spermatozoa, including their swimming behaviour in relation with their energetic content (ATP) and their ability to be sustained by mitochondrial respiration, in a comparative way with other marine animals.