Osmolality and Potassium Ion: Their Roles in Initiation of Sperm Motility in Teleosts

Abstract

Spermatozoa that are quiescent in electrolyte and nonelectrolyte solutions isotonic to seminal plasma show motility when the semen is diluted with hypotonic solution in freshwater teleosts (four species tested) and with hypertonic solution in marine teleosts (five species tested). Decrease or increase, respectively, in osmolality of the environment may be the factor initiating sperm motility in these species. The motility of chum salmon spermatozoa in a sodium chloride solution isotonic to seminal plasma is completely suppressed by approximately 10 millimoles of potassium per kilogram; topminnow spermatozoa, however, were immotile in a nonelectrolyte solution, and motility was induced by electrolytes, especially potassium. Thus ions, rather than osmolality, may be an essential determinant of sperm motility in salmonid and viviparous teleosts.

Development of a simplified and standardized protocol with potential for high-throughput for sperm cryopreservation in zebrafish Danio rerio

“…The motility of zebrafish sperm decreased as the osmolality of the extender solution increased, and was completely inhibited at osmolalities of 300 mOsomol/kg and above. This agreed with the plasma osmolality (296 ± 8 mOsmol/kg), and is typical for the sperm of most freshwater fishes [9][10][11]. Fish sperm are usually immotile in the testis [10], and motility is controlled by factors such as osmolality, ions, temperature, and pH [9,12,13].…”

“…Osmolality is the dominant factor in most species studied. In general, motility of sperm from freshwater fish is initiated by hypotonic solutions, and motility of sperm from marine fish is initiated by hypertonic solutions [10]. A third modality is where motility is initiated when osmolality is isotonic to that of the plasma, a condition that has been described for live-bearing fishes [14].…”

Intracellular changes in Ca2+, K+ and pH after sperm motility activation in the European eel (Anguilla anguilla): Preliminary results

“…In marine teleosts, spermatozoa are quiescent in isotonic solutions, such as seminal 43 plasma, and become motile in contact with hypertonic solutions, suggesting that 44 motility is suppressed by the seminal plasma osmolality that is initiated by exposure to 45 hypertonic seawater at spawning (Morisawa and Suzuki, 1980 …”

Involvement of redox- and phosphorylation-dependent pathways in osmotic adaptation in sperm cells of euryhaline tilapia

“…Indeed, the stimuli for its activation differ between freshwater and marine teleosts: hypotonic shock activates motility in the sperm of freshwater teleosts, whereas hypertonic shock produces a similar effect in the sperm of marine teleosts (Morisawa and Suzuki, 1980;Oda and Morisawa, 1993). These osmolality-dependent responses are thus specialised to the different habitats.…”