Sperm traits and fertilization success of male and sex-reversed female rainbow trout (Oncorhynchus mykiss)

Sperm motility, density, adenosine triphosphate (ATP) concentration, and fe rtilization rates of sex-reversed female (XX-male) rainbow trout (Oncorhync hus mykiss) were compared to those of normal (XY-male) males. The relations hips between sperm traits, fertilization rates, and characteristics of indi vidual fish (weight, gonadosomatic index) were assessed. The fertilization rate of sperm stripped from normal males averaged 81% (s.d. 16%). The sperm of sex-reversed females had to be removed directly from the testes and ach ieved average fertilization rates of 60% (s.d. 13%), Testicular sperm from normal males was motile for shorter periods of time and produced lower fert ilization rates than testicular sperm from sex-reversed fish. Fertilization rates were positively correlated with higher initial sperm motility, but n ot with sperm density or ATP concentrations. (C) 2000 Elsevier Science B.V. All rights reserved.