Fig. 2. Effect of partial pressure of oxygen on the mating behaviour (non-competitive environment) of male eastern mosquito fish Gambusia holbrooki acclimated to either hypoxic or normoxic conditions for at least 6 weeks. (A) The total time males spent following females, (B) total number of attempted copulations and (C) the total number of successful copulations recorded during a 10 min observation period in a non-competitive environment. Values are means ± s.e.m., N=15 for each acclimation group. ^*Significant results at P<0.05.