50 SEPTEMBER 2013 • WORLD AQUACULTURE • WWW.WAS.ORG Summary and Information Gaps Sperm motility activation is a very complex and highly organized process involving reception of an external activating signal, its transduction to axonemal machinery and, ultimately, activation of axonemal dyneins (Fig. 4). The nature of external activating signals can vary significantly among species of fish. The signal may be a change of osmolality, K+, Ca2+, Mg2+ and other cation concentrations in the external milieu, egg-derived spermactivating substances, gaseous components of the external media or specific proteins from egg chorion or present in seminal plasma. Reception (or sensing) of external signals takes place at the level of the spermatozoa plasma membrane and several participants are involved in this process. Different ionic channels, aquaporins and ion receptors share signal reception. The reception of external stimuli is followed by signaling conducted by a second messenger (cAMP, Ca2+, reactive oxygen and nitrogen species) leading to axonemal movement through activation of axonemal dyneins by protein phosphorylation or dephosphorylation signals. The precise tuning of the orchestrated process leading to sperm motility activation is not yet fully understood in fish. The final steps of motility activation signaling is the most intriguing field of flagella activity studies. While some distinct processes of flagellar micro-machinery activity are already well described, detailed investigation of the control of fish sperm flagella beating requires modern techniques for better understanding of the relationships among axonemal super-molecular structures. The energy source for flagella activity is hydrolysis of ATP, the metabolic pathways involved in its production and distribution along the entire length of flagellum are taxa-specific. Accumulation of knowledge focused on the role of carbohydrates and lipids in ATP production, creatine-phosphate shuttle and adenylate kinase activities in different species is required. Better understanding of all steps involved in fish sperm motility activation and maintenance will lead to improved sperm manipulation conditions in aquaculture. Practical Implications for Aquaculture The main goals of studies on fish sperm motility often consist of finalizing a solution that prevents motility to save sperm for various periods of time while preserving potential motility, or developing a solution that allows activation and maintenance of motility for as long a period as possible to increase the fertilization rate. A general strategy consists of varying parameters one by one, such as osmolarity or the concentration of specific ions, among which potassium (K+) and calcium (Ca2+) should be tested first. Another rule-of-thumb is to design a non-swimming solution according to the concentration of the main components of seminal fluid, as estimated by chemical analysis of its soluble components. Design of the swimming solution should first consider assessment of gross motility parameters, such as percentage of motile cells in a medium with a composition close to the natural spawning milieu. Notes Jacky J. Cosson, University of South Bohemia in Ceske Budejovice, Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, 38925 Vodnany, Czech Republic. jacosson@gmail.com. Website showing video record of fish sperm while moving: server3.streaming.cesnet.cz/others/jcu/vurh/filmy/windowsmedia/ spz-01.wmv 1 Phosphorylation consists of binding one (possibly several) phosphate residues on an enzymatic protein, which is sufficient to render such protein active or inactive. Acknowledgments We are thankful to Galina Prokopchuk for allowing us to publish the document in Figure 2a and to Monik Cosson for help in the finalization of the manuscript. Special thanks are also expressed to Czech Agencies for support of the projects CENAKVA CZ.1.05/2.1.00/01.0024, GAJU 046/2010/Z, GACR P502/11/0090 and GACR P502-12-1973. References Abascal, F. J., J. Cosson and C. Fauvel. 2007. Characterization of sperm motility in European seabass. The effect of heavy metals and physicochemical variables on sperm motility. Journal of Fish Biology 70:509-522. Aitken, R.J. and L. Bennetts. 2006. Reactive oxygen species: friend or foe. Pages 170-193 In De Jonge, C.J. and Barratt, C.L.R., editors. The Sperm Cell. Production, Maturation, Fertilization, Regeneration. Cambridge University Press, New York. USA. Alavi, S.M.H. and J. Cosson. 2005. Sperm motility in fishes. I. Effects of temperature and pH: a review. Cell Biology International 29:101-110. Alavi, S.M.H. and J. Cosson. 2006. Sperm motility in fishes. II. Effects of ions and osmolality: a review. Cell Biology International 30:1-14. Billard, R. 1970 Ultrastructure comparée de spermatozoides de quelques poisons téléostéens. Pages 71-80 In B. Baccetti editor. Spermatologia comparata. Quaderno 137, Academia Nazionale dei Lincei, Roma, Italy. Billard, R., J. Cosson, F. Fierville, R. Brun, T. Rouault and P. Williot. 1999. Motility analysis and energetics of the Siberian sturgeon Acipenser baerii spermatozoa. Journal of Applied Ichthyology 15:199-203. Cosson, J. A.-L., Groison, M. Suquet, C. Fauvel, C. Dreanno and R. Billard. 2008a. Studying sperm motility in marine fish: an overview on the state of the art. Journal of Applied Ichthyology 24:460-486. Cosson, J., A.-L. Groison,M. Suquet, C. Fauvel, C. Dreanno and R. Billard. 2008b. Marine fish spermatozoa: racing ephemeral swimmers. Reproduction 136:277-294. Cosson, J. 2010. Frenetic activation of fish spermatozoa flagella entails short-term motility, portending their precocious decadence. Journal of Fish Biology 76:240-279. Cosson, J., C. Dreanno, R. Billard, M. Suquet and C. Cibert. 1999. Regulation of axonemal wave parameters of fish spermatozoa by ionic factors. Pages 161-186 In C. Gagnon, editor. The male gamete: from basic knowledge to clinical applications. Cache River Press, Montréal, QC. Canada. Cosson, J. 2008a. Methods to analyze the movements of fish spermatozoa and their flagella. Pages 63-101 In S.M.H Alavi,.
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