Fig. 2. Electro-olfactograms (EOGs) recorded from male tilapia in response to extracts of female water. (A) Typical EOGs recorded in response to pooled extracts of water (diluted 1:100) from pre-ovulatory (shaded horizontal bar, left panel) and post-ovulatory (shaded horizontal bar, right panel) females. A downward deflection of the EOG trace is negative. (B) Semi-logarithmic plot of pooled normalized EOG amplitudes (N=6) to pooled extracts of female water from pre-ovulatory (filled circles) and post-ovulatory (open circles) females at three dilutions. An equivalent dilution to give the same concentration as the original water sample would be 1:2000. ^***P<0.001.