Effects of gonadotropin-releasing hormone analog on milt production
enhancement in starry flounder Platichthys stellatus
Han
Kyu Lim, Hyon Sob Han, Young Jin Chang-2002
Fisheries
Science, 68(6):
1197-1204
Abstract:
The
treatment of exogenous gonadotropin or gonadotropin-releasing hormone analog
(GnRHa) is able to solve some problems that are caused by small milt volume
or viscous milt in artificial insemination of flatfish species. However, the
mechanism of the action of the exogenous hormones on milt production has not
been well understood. Therefore, experiments were carried out to study the
effects of GnRHa on the milt production and characteristics of seminal
plasma in starry flounder Platichthys stellatus. Males were implanted
with GnRHa pellets at three different dosages (50, 100 or 200
g/kg
body weight) during their natural spawning season. Milt volume and sperm
production increased in a dose-dependent manner after GnRHa pellet
treatments. Spermatocrit and sperm concentration were significantly lower in
GnRHa treated groups than in the control group. The sperm motility index was
high from day 4 to day 49 in all experimental groups including the control
group, and it declined after day 49 in all groups except the 200
µg
treated group in which it remained high until day 85. During the
experimental period, osmolality, K+ and total protein tended to
be higher in the control group than in the GnRHa treated groups. The results
suggested that GnRHa treatment increased the milt volume and sperm
production ability in starry flounder. The increase of milt volume was twice
as rapid as the increase of sperm production. No significant differences in
physicochemical composition of blood plasma and seminal plasma were found
according to GnRHa dosages, but there were significant differences between
GnRHa treated groups and the control group.
(Uljin Marine Hatchery, National Fisheries Research
and Development Institute, Osan, Wonnam, Uljin-gun 767-860, Korea, e-mail of
Young Jin Chang: yjchang@pknu.ac.kr)