Hypothermic storage in salt-free preservative solution alter motility duration in sterlet sperm

Abstract

Together with concentration, motility is one of the most important characteristics of sturgeon sperm, determining its quality and suitability for insemination. After activation in water, the duration of progressive sperm motility is also important, and this time should not be less than that required for fertilization. Motility of spermatozoa depends on their physiological state, maturity, age and intracellular reserves of macroergic substances. During hypothermic storage, the percentage of spermatozoa that can be activated decreases progressively due to depletion of ATP supply or cell death. To improve the hypothermic storage of sterlet sperm, we have developed salt-free preservative solution ISGT-80 based on glucose and trehalose. During storage of sterlet sperm specimens from 20 males in ISGT-80 for 18 days, we observed, along with a progressive decrease in the percentage of motile spermatozoa, an alteration in the duration of their motility. On the 3rd to 6th day of storage, the time of half-loss of motility (τ50) increased significantly by approximately 1 min on average compared with fresh samples, then gradually decreased, however, not descending to the initial value. The reasons for this prolongation of motility are not clear, but we do not exclude the predominant death of spermatozoa with a short motility duration in the first days of storage and selection in favor of long-lived spermatozoa. Such gametic selection can lead to a shift in allele frequencies at heterozygous loci in the offspring. Thus, hypothermic storage of sperm could become an attractive subject for genetic research with the aim of developing new selection tools in sturgeon breeding.