Sperm metabolism of the teleost fishes Chalcalburnus chalcoides and Oncorhynchus mykiss and its relation to motility and viability

In the teleost fish Chalcalburnus chalcoides (Cyprinidae) the influence of metabolic inhibitors, substrates, coenzymes, and oxygen concentrations on s permatozoal parameters during motility and during immotile incubation was s tudied, the respiration rate was characterized, representative metabolite l evels were measured, and the results were compared with Oncorhynchus mykiss (Salmonidae). In Chalcalburnus chalcoides the sperm motility rate, the average path swimm ing velocity, the motility duration, and the viability of immotile semen we re significantly reduced in the presence of inhibitors of respiration (pota ssium cyanide, 2.4-dinitrophenol, atractyloside). Anaerobic conditions (<1 mg O-2/liter) and inhibition of the tricarboxylic acid cycle by malonate an d >7.5 mmol/ liter succinate had similar effects on the sperm motility para meters and on the viability of immotile spermatozoa. Pyruvate and coenzyme A (an acyl-group carrier during oxidative carboxylation of pyruvate) prolon ged the duration of sperm motility and the viability of immotile incubated spermatozoa, and also increased the spermatozoal respiration rate. Glucose levels significantly decreased during motility and during immotile storage and, under anaerobic conditions, the levels of lactate increased indicating that pyruvate derived from glycolysis. The respiration rate and the glycol ytic rate significantly increased during motility. Therefore oxidative phos phorylation, tricarboxylic acid cycle, and aerobic glycolysis are central, energy-supplying pathways for spermatozoa of Chalcalburnus chalcoides. The stimulatory effect; of pyruvate and coenzyme A indicated that glycolysis is a rate-controlling pathway. Similar results were obtained for Oncorhynchus mykiss with the only exception that the stimulatory effect of coenzyme A w as more significant than the stimulatory effect of pyruvate. When the sperm motility-activating saline solutions were optimized in aspec ts of energy supply, ionic composition, and osmolality, about; 50% of the m otile spermatozoa swam progressively (>20 mu m/sec) for about 3 min in Chal calburnus chalcoides and in Oncorhynchus mykiss. About 20% swam progressive ly for >2 hr in Chalcalburnus chalcoides and for >30 min in Oncorhynchus my kiss. J. Exp. Zeal. 284:454-465, 1999. (C) 1999 Wiley-Liss, Inc.