Seasonal variations in sperm production and sperm quality in male winter flounder, Pleuronectes americanus: the effects of hypophysectomy, pituitary replacement therapy, and GnRH-A treatment |
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Authors: | B Shangguan L W Crim |
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Institution: | (1) Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X9, Canada, CA |
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Abstract: | The pattern of sperm release and changes in sperm quality were investigated throughout the normal spawning season of male
winter flounder, Pleuronectes americanus (Walbaum), caught in Conception Bay, Newfoundland, Canada in April and November 1994. In addition, the impact of hormonal
manipulation on sperm production and sperm quality was examined through gonadotropin-releasing hormone analogue (GnRH-A) treatment,
hypophysectomy, and pituitary extract injection – pituitary replacement therapy (PRT). While a lengthy period of spermiation,
lasting ∼6 months (December to July), can be detected in some males, the major period for sperm release occurred in May to
July in the summer spawning season. The spawning period started with peak levels of plasma testosterone (T) and 11 ketotestosterone
(11-KT). By late July sperm production fell rapidly along with a notable deterioration in sperm motility. While GnRH-A treatment
advanced the period of sperm release, and the milt became diluted and increased in volume, the treatment did not increase
total sperm output over the spawning season. In hypophysectomized male flounder, by contrast, milt was more concentrated and
sperm production declined along with reduced plasma androgen levels during the spawning season. Increased plasma T and 11-KT
levels in hypophysectomized males followed PRT in December and January. Moreover, PRT appeared to be responsible for advancement
of spermiation in a large number of prespawning males, which released an increased amount of milt. Finally, these studies
indicated that both sperm motility and egg fertilization rates remained unchanged after these hormonal treatments.
Received: 5 September 1997 / Accepted: 6 January 1999 |
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