Abstract

Calcium is a prerequisite factor for triggering the sperm activation in salmonids. The aim of this study was to test different concentrations of Ca(2+)on sperm motility activation and fertility of rainbow trout (Oncorhynchus mykiss). Semen samples activated with calcium free activator (0.0 mM) and increasing concentrations of CaCl2(6.3, 7.9, 9.5 and 11 Mm) were evaluated by computer-assisted sperm analysis (CASA). To assess fertility, eggs from three females were fertilized with semen and activated with each of the five solutions and incubated until four-cell stage when the rate fertility and the symmetry of the first blastomeres were evaluated. The results show that eliminating calcium from the activator solution significantly reduced the motility rate and fertility in comparison with the other treatments, while increasing the CaCl(2)from 6.3 to 11 mM generated high sperm motility (78.5 +/- 5.8-95.4 +/- 4.0%) and fertility (85.0 +/- 9.3-96.0 +/- 6.51%) rates, and low symmetry rates in the first blastomeres (<20%). No significant differences were found between solutions for the latter two variables, suggesting that the calcium concentrations were in balance with the other components of the medium and within the requirements for the fertilization of rainbow trout.