Standardization of photometric measurement of sperm concentration from diploid and tetraploid Pacific oysters, Crassostrea gigas (Thunberg)

To provide necessary standardization of procedures for cryopreservation of sperm, a spectrophotomeric method was developed to determine the sperm concentration of diploid and tetraploid Pacific oysters, Crassostrea gigas . Wavelengths of 380, 550, 581 and 780 nm were compared, and 550 and 581 nm were found to be the most sensitive and reliable. A linear relationship between sperm concentration and photometric absorbance was observed for sperm concentrations between 2 × 10 7 and 2 × 10 9  cells mL −1 . The regression equation for the standard curve at 550 nm for sperm of diploid oysters was Y =−8.528+1.165 log  X . The equation for sperm of tetraploid oysters was Y =−8.844+1.236 log  X . The equation at 581 nm for sperm of diploid oysters was Y =−8.07+1.104 log  X . The equation at 581 nm for sperm of tetraploid oysters was Y =−8.331+1.167 log  X . Comparisons derived from the standard curves at 581 nm between observed values and the predicted values indicated good agreement for sperm from diploid (coefficient of determination, r 2 =0.983) and tetraploid ( r 2 =0.980) oysters.