Cultivated male Japanese eels [200-300 g body weight (bw)] are sexually immature and do not mature under normal culture conditions. Injecting them with gonadotropins, however, can easily induce maturation (Yamamoto et al. 1972; Miura et al., 1991) and spermiation (Ohta et al. 1996). Administration of androgens can also induce maturation even at their juvenile stage (Ohta and Takano 1996). Sperm cells that have completed their spermatogenesis in the testis are immotile when diluted with seawater, but they acquire the potential for motility upon transfer from the testicular lumen to the sperm duct (Ohta et al. 1997a). Because a relationship between motility and the capacity for the fertilization of teleost spermatozoa has been confirmed by many authors (Billard and Cosson 1992; Lahnsteiner et al. 1996), the acquisition of motility by spermatozoa can be defined as the functional maturation of the spermatozoa. We have developed techniques for acquiring adequate quantities of high-quality spermatozoa for successful artificial fertilization.
KeywordsSperm Cell Sperm Motility Seminal Plasma Genital Pore Sperm Maturation
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