Abstract:
Ocellate river stingray (Potamotrygon motoro) is one of the ornamental fish trade in Thailand. There is no data about reproductive system. The aims of this study were to: 1) develop a method of semen collection in this species, 2) study sperm morphology, 3) evaluate fresh semen quality, 4) test the effects of some extenders and find the ratio of semen:extender during chilled storage at 4 ºC on sperm motility and viability and 5) test the effects of some extender-cryoprotectant combinations during freezing at -196 ºC on sperm motility and viability. The utilities could be used to choose a good male stingray for breeding, develop protocol of semen preservation and apply in artificial insemination for freshwater stingray in the future. Semen was collected from 10 adult male stingrays by the gloved-hand method with no anesthesia. Fresh semen was evaluated for the semen quality and sperm morphology. Then, the semen was diluted in different kinds of extender and cryoprotectant for chilled and frozen preservation. The examined extenders included Hank's Balanced Salt Solution (HBSS), Calcium-Free Hank's Balanced Salt Solution (Ca-F HBSS), Normal Saline Solution (NSS) and Modified Fish Ringers Solution (MFR). The cryoprotectants were 5% Glycerol, 10% Glycerol, 5% (Dimethyl sulfoxide) DMSO and 10% DMSO. In this study, it was found that the fresh motoro semen was white and creamy. Semen volume was 0.53±0.15 mL. pH was 7.3±0.26. Sperm density was 2.28±0.46 x109 sperms/mL. Sperm motility was 98.5±2.42%. Spermatocrit was 15.4±2.88%. Sperm viability was 89.8±3.36%. Size of spermatozoon was 116.34±1.92 µm in length. It had twisted head with pointed anterior tip and blunted posterior end. It had spiral movement. Sperm from fresh semen was alive for 6 days. In chilled storage at 4 ºC, Ca-F HBSS was used as a basis extender at 1:1. Sperm was alive for 11 days. In freezing storage at -196 ºC, semen was preserved in liquid nitrogen for 2 weeks. After thawed in water bath, the results showed that preserved semen in 5% Glycerol had the statistically best efficacy (P<0.05). Sperm motility was 42.0±3.50% and Sperm viability was 42.9±2.85%.