The effect of different ambient temperatures on river lamprey (Lampetrafluviatilis) egg and sperm production under controlled conditions

Reproductive performance (ovulation/spermation rate and relative fecundity of females) of adult river lamprey (Lampetrafluviatilis) was compared among adults held under three different controlled thermal regimes (7, 10 and 14 °C). The quantity of semen (volume of semen, sperm concentration, total sperm production and total number of sperm) and the weight of the eggs as well as the semen quality (sperm motility, seminal plasma osmolality and pH, sperm pH and total protein content) were determined. Housing temperature had no apparent effect on quality or quantity of eggs produced, but did influence time of ovulation. On the other hand, temperature had a significant effect on the quantity and quality of sperm produced; 70% of males held at 10 °C and 14 °C did not spermiate. The best ambient temperature for river lamprey adults held under controlled conditions was 7 °C. All males kept in this temperature yielded mature semen with the highest sperm motility parameters. It was also found that among the six tested solutions, the most suitable artificial medium for river lamprey sperm activation was 20 mM Tris buffer containing 40 mM NaHCO3 at pH 8.5 and 100 mOsm kg−1.