Artificial maturation of female Japanese eels by the injection of salmonid pituitary

Oogenesis in Teleost Fish

“…Even in female silver eels migrating down rivers for spawning in fall, GSI are 1-2% (Yamamoto et al 1974a) and they have ovaries containing oocytes at the oil stage or oocytes at the primary yolk globule stage (Yamamoto et al 1974b). New Zealand longfinned eel, Anguilla dieffenbachii, have ovaries containing oocytes at the mid-vitellogenic stage and their GSIs are about 7% (Lokman et al 1998).…”

“…New Zealand longfinned eel, Anguilla dieffenbachii, have ovaries containing oocytes at the mid-vitellogenic stage and their GSIs are about 7% (Lokman et al 1998). However, cultivated and wild silver eels do not mature and ovulate under normal culture conditions (Yamamoto et al 1974a;Dufour et al 1988). Moreover, as most cultivated eels are male (Chiba et al 1993), it is difficult to obtain a large number of females for experimental purposes.…”

“…SPE was prepared by homogenizing salmon (Oncorhynchus keta) pituitary powder with 0.9% NaCl solution, followed by centrifugation at 9,700 × g (Kagawa et al , 1998aOhta et al 1996a). Repeated weekly injections of SPE over 10 weeks efficiently induced vitellogenesis, resulting in the female eels reaching at full-grown oocytes at the migratory nucleus stage (Yamamoto et al 1974a;Yamamoto and Yamauchi 1974;Ohta et al 1996a;Kagawa 2003;Kagawa et al 2005). However, their oocytes do not undergo maturation and become over-ripe with oocyte cytoplasmic degeneration in response to further injections of SPE.…”

Morphological and histological changes in the swim bladder during maturation of the Japanese eel

“…Eels were matured artificially by injecting a saline suspension of chum salmon Oncorhynchus keta (Walbaum) pituitary to various maturation stages up to spawning (20 mg kg 1 body weight, once a week) based on the reported method (Yamamoto et al, 1974b).…”

Water temperature manipulation can induce oocyte maturation and ovulation in the common Japanese conger, Conger myriaster

“…In anguilliform fish, artificial maturation techniques have been improving markedly, although these methods depend on exogenous hormone treatments Boëtius, 1967, 1980;Horie et al, 2001Horie et al, , 2003Horie et al, , 2008Lokman et al, 2001;Ohta et al, 1996;Yamamoto et al, 1974). However, little is known regarding the maturation process containing endocrine conditions without exogenous hormone treatments because the majority of oocyte development occurs during the spawning migration, which has yet to be described in anguilliform fishes.…”