Publication Abstract

Fertility and motility of sperm from Atlantic halibut (Hippoglossus hippoglossus) in relation to dose and timing of gonadotrophin-releasing hormone agonist implant

Fertility and motility of sperm from Atlantic halibut (Hippoglossus hippoglossus) in relation to dose and timing of gonadotrophin-releasing hormone agonist implant

E.L.M. Vermeirssen, C.M. de Quero, R.J. Shields, B. Norberg, D.E. Kime and A.P. Scott

Male Atlantic halibut were implanted intramuscularly with pellets containing gonadotrophin-releasing hormone agonist (GnRHa). The effect of the pellets was tested at three periods: before, at the height of and at the end of spermiation. In the middle period, GnRHa was tested at two doses (5 and 25 µg/kg bodyweight). Measurements were made of milt hydration, sperm motility and fertilisation rate. Implanted males began spermiation at least 4 weeks before control males. Both doses of GnRHa increased the fluidity of the milt. This effect lasted for at least 20 days in the low dose group and for 40 days in the high dose group. When applied at the end of the season, GnRHa reversed the normal trend for the milt to become more viscous. GnRHa treatments did not affect fertilisation rates obtained with the sperm. However, towards the end of the spawning season, motility was enhanced in males treated with the high dose of GnRHa (25 µg/kg) compared to controls. As described previously, plasma concentrations of the gonadal steroids 5b-pregnane-3b,17,20b-triol 20-sulphate and 17,20b-dihydroxy-4-pregnen-3-one, were significantly enhanced by GnRHa treatment. Concentrations of testosterone on the other hand decreased when spermiated males were treated with GnRHa. Our data suggest that 17,20b-P or its metabolites are involved in milt hydration, possibly through affecting ion transport.

Reference:

E.L.M. Vermeirssen, C.M. de Quero, R.J. Shields, B. Norberg, D.E. Kime and A.P. Scott (2004) Fertility and motility of sperm from Atlantic halibut (Hippoglossus hippoglossus) in relation to dose and timing of gonadotrophin-releasing hormone agonist implant. Aquaculture, 230: 547-567

E.L.M. Vermeirssen, C.M. de Quero, R.J. Shields, B. Norberg, D.E. Kime and A.P. Scott*

Aquaculture, 230: 547-567