Initiation of sperm motility depending on a change in external osmotic pressure in the noncopulatory marine cottid fish Gymnocanthus herzensteini

Abstract

The initiation of sperm motility in a noncopulatory marine cottid fish, Gymnocanthusherzensteini, was examined. The spermatozoa, which were immotile in seminal plasma, initiated motility at osmolalities of more than 500 mOsm kg−1 in NaCl solution and 400 mOsm kg−1 in KCl and mannitol solutions, indicating that the initiation of sperm motility depends on changes in external osmolality, in contrast with that of the sperm of other marine cottid fish, which are motile in seminal plasma. This study revealed that there are plural manner of initiation of sperm motility in marine cottid fish, which are oviparous but include both copulatory and noncopulatory modes.