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Abstract
The objective of the present study was to assess the effects of dilution ratios, osmolality and cations on sperm motility of sea urchin Trippneustes gratila (Linnaeus, 1758). Sperm was diluted in artificial seawater (ASW) at ratios of 1:1; 1:25; 2:50; 1:100 and 1:200 (sperm: ASW) to determine the best ratio dilution for sperm motility. Then, the best ratio was used for the osmolality experiment (100, 200, 300, 400 và 500 mOsm/kg). Each treatment was replicated three times. The result showed that sperm motility of sea urchin was the best dilution ratio and osmolality at 1:50 and 500mOsm/kg, respectively. These results indicate that the sperm of sea urchin can be active at an osmolality medium of 500 mOsm/kg when diluted at the ratio of 1:50 (semen:medium).