Aging Processes of Rainbow Trout Semen during Storage

Abstract

Changes in fertility, motility, sperm metabolism, and seminal plasma composition during 2-h in vitro storage on ice (2 mL semen in a 10-mL centrifuge tube with a diameter of 1 cm) were investigated for semen from rainbow trout Oncorhynchus mykiss. After 2 h, the fertilization capacity was reduced by about 35%, motility rate by 65%, and swimming velocity by 26% in comparison with freshly collected semen. The seminal fluid osmolality and sodium and potassium concentrations decreased, while the spermatozoan sodium and potassium levels increased, indicating ion influx into the cells. The increase in glycerol, fatty acid, and triglyceride levels of the seminal fluid and of the spermatozoa indicated aging of semen. Spermatozoan adenylate kinase, malate dehydrogenase, and respiratory activities, and thus energy requirements of semen, were high after 2-h semen storage compared with fresh semen. Spermatozoa used glucose for energy supply as its levels decreased. Adenosine triphosphate, NADH, and lactate levels remained constant. Fertilization rate correlated significantly (P < 0.005, N = 64) with the sperm motility rate (r = 0.655), sperm swimming velocity (r = 0.376), seminal fluid composition (pH, r = 0.462; osmolality, r = 0.228; sodium, r = 0.247; potassium, r = 0.239; calcium, r = -0.244), and sperm metabolism (malate dehydrogenase, r = -0.754; respiration activity, r = -0.495; adenosine triphosphatase, r = 0.267).