Abstract
To determine the effect of male pheromone stimuli on ovarian development in female Nile tilapia (Oreochromis niloticus), changes in gonad-somatic index (GSI), oocyte diameter, and plasma estradiol-17β (E2) were investigated at 20, 40, 60, and 80 days during the rearing in the experimental tanks in which the female were treated with five kind of male (M) stimuli: (K-0) no stimulus as control (no contact with M), (K-1) only visual stimulus (separated from M by the transparent glass partition), (K-2) only olfactory stimulus (separated from M by the opaque partition with some small holes), (K-3) both visual and olfactory stimuli (separated from M by the transparent partition with some small holes), (K-4) all visual, olfactory, and skin contact stimuli (together with M).
The experimental results demonstrated that GSI, oocyte diameter, and E2 in K-2, K-3, and K-4 were significantly higher than those in K-0 at and after 40 days (p<0, 05). There was little difference between K-0 and K-1. Therefore, the ovarian development was strongly affected by olfactory stimulus (male pheromones), but not by visual stimulus.
