Effect of pH, osmolality and temperature on sperm motility of pink cusk-eel (Genypterus blacodes, (Forster, 1801))

In this research we evaluated simple aspects of the sperm biology of Genypterus blacodes, in particular assessing the effects of pH (6, 7, 8 and 9), temperature (4, 8 and 16 degrees C) and osmolalities 100% sea water (1010 mOsm/kg, Control), 75% sea water (774 mOsm/kg, T-1), 50% sea water (488 mOsm/kg, T-2) and distilled water (0 mOsm/kg, T-3)) on the motility of Genypterus blacodes intratesticular spermatozoa. In addition, we determined the fertilization rate. Our results show that G. blacodes spermatozoa have a sperm density of 5.35 +/- 0.16 x 10(9) spermatozoa/mL. Sperm motility is initiated on contact with a hyperosmotic swimming medium under normal conditions (1010 mOsm/kg, pH 8 and 8 degrees C). The longest motility duration (432.48 +/- 8.89 s) was recorded at 4 degrees C. The maximum percentage of motile cells was recorded at 8 degrees C (65.66 +/- 4.95) at osmolality 1010 mOsm/kg, whereas an optimum was observed at pH 8. The fertility rate was 73.9 +/- 17%. This is the first report on sperm motility of G. blacodes spermatozoa. In conclusion, the results of this study permit a baseline to be established for further research and protocols for artificial reproduction of this species to be developed and optimized. In addition, the information gathered in this research will be useful for developing the biotechnology of Genypterus blacode