Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2423889 | Aquaculture | 2009 | 6 Pages |
The purpose of this study was to examine the effects of continuous administration of human chorionic gonadotropin (HCG), salmon pituitary extract (SPE), and gonadotropin-releasing hormone analogue (GnRHa) via an osmotic pump with a long-term sustained hormone-release system on the induction of sexual maturation in male Japanese eels (Anguilla japonica). Implantation of a single HCG-loaded osmotic pump induced spermatogenesis and increased the gonadosomatic index (GSI) values at 35–42 days postimplantation; GSI values were higher (10.7 ± 1.0) than those of the fish implanted with a cholesterol pellet containing HCG (2.4 ± 0.6). Implantation of an SPE-loaded osmotic pump also stimulated spermatogenesis, although the GSI values were lower than those of the fish implanted with the HCG-loaded osmotic pump. Implantation of a single osmotic pump loaded with various doses of GnRHa (0.94, 1.86, or 3.75 µg/day) did not stimulate spermatogenesis. The GSI values and milt weight of the HCG-administered eels significantly increased at a dosage of 5 IU/day in a dose-dependent manner up to 50 IU/day. Sperm motility was not significantly different among the eels treated with different doses of HCG. Therefore, implantation of a single osmotic pump loaded with HCG (50 IU/day) is a reliable method for inducing spermatogenesis and spermiation in sexually immature Japanese eels.