Factors Affecting Motility Characteristics and Fertilizing Ability of Sea Lamprey Spermatozoa
Summary
Abstract.—This study was conducted to determine the basic motility characteristics of the spermatozoa (hereafter, sperm) of sea lampreys Petromyzon marinus using computer-assisted motility analysis. We determined the effects of NaCl, KCl, and pH on semen motility. We also tested the effects of time after activation and sterilization on sperm motility and fertilizing ability. Sperm motility was inhibited by high osmolality (80 mM NaCl or KCl). There were inverse relationships between the NaCl concentration and straight-line velocity (VSL; r2 5 0.97, P , 0.01) and linearity (LIN; r2 5 0.81, P , 0.05). The duration of sperm motility decreased with increases in pH. Positive linear relationships were obtained between pH and VSL (r2 5 0.79, [...]
Summary
Abstract.—This study was conducted to determine the basic motility characteristics of the spermatozoa
(hereafter, sperm) of sea lampreys Petromyzon marinus using computer-assisted motility
analysis. We determined the effects of NaCl, KCl, and pH on semen motility. We also tested the
effects of time after activation and sterilization on sperm motility and fertilizing ability. Sperm
motility was inhibited by high osmolality (80 mM NaCl or KCl). There were inverse relationships
between the NaCl concentration and straight-line velocity (VSL; r2 5 0.97, P , 0.01) and linearity
(LIN; r2 5 0.81, P , 0.05). The duration of sperm motility decreased with increases in pH. Positive
linear relationships were obtained between pH and VSL (r2 5 0.79, P , 0.01) and LIN (r2 5
0.78, P , 0.01). Sperm motility decreased with time; a 50% decrease in motile cells was observed
4 min after activation; after 10 min, only 7% of the sperm were still motile. Fertilizing ability
declined to 27% after a 2-min exposure and to 0.4% after 4 min. Sperm motility was prolonged
in the presence of substances produced by females, either coelomic fluid or egg water. Semen from
males treated with bisazir (a sterilant) was similar to that of the control treatment in sperm
concentration, motility, and fertilization rate; however, almost no hatched larvae were observed.
Our results indicate that sea lamprey sperm are kept immotile by rather high osmolality. The
duration of sea lamprey sperm movement is among the longest of freshwater fish. Motility characteristics
may be modulated by sodium and potassium ions and pH. A peculiar characteristic of
sea lamprey sperm is the presence of oval-shaped blebs on the tail. These results provide a basis
for future evaluation and control of the reproductive function in sea lampreys.