Effects of extracellular environment factors on the motility in Japanese eel spermatozoa

We have examined the effects in vitro of the ionic composition, pH and temperature on the motility by the spermatozoa of the Japanese eel (Anguilla japonica). Milt was obtained from 10 males that had been artificially matured by repeated injections of hCG. Sperm motility was monitored with a VHS video recorder and a video camera connected to a microscope. The results showed that most of the sperm were highly motile in 250-700 mM NaCl, 250-650 mM KCl and 350-550 mM CaCl2 solution. The longest duration of sperm motility recorded in 500 mM NaCl, 250 mM KCl and 350 mM CaCl2 solution. Sperm was not motile when suspended at pH 2, sperm motility was observed at pH 3, there was a relatively higher percentage of motile sperm in solutions at pH 4-12 (above 80%). The motility and duration increased within 18-24°C and decreased at the range of 24-30°C. Appropriate K+ ion concentration in the active medium could enhance the percent motility and duration of eel spermatozoa.