| The Lota lota is an important economical cold water fish in Irtysh River Basin. In recent years, number of the wild Lota lota is gradually reduced, and departments concerned are carrying out related works for lota lota protection and its aquaculture development. Fewer lota lota fry is a main problem that has plagued the artificial restocking and culture promotion of lota lota. Therefore, studies on the sperm motility of Lota lota are of significant importance. In this paper, individual effects of six factors, namely, Na+, K+, Ca2+, glucose, fructose, and pH, on sperm motility of Lota lota were explored, response surface analysis of three important factors including Na+, glucose, and pH was optimized, and artificial insemination tests with both single activation solution and compound activation solution were performed in order to improve the fertilization rate of Lota lota. The main results of this study are as follows:(1) The test results of six factors of Na+, K+, Ca2+, glucose, fructose, and pH alone acting on sperm motility showed that:the sperm activation rate reached 90%when the concentration of Na+ was 45 mmol·L-1, with the maximum FT and LT values of 44.26±2.72 s and 77.42±4.55 s, respectively. The sperm activation rate reached 80%at 5 mmol·L-1 K+ with the maximum FT and LT values of 28.4±3.47 s and 45.64±6.62 s. The sperm motility in Ca+solution peaked at concentration of 30 mmol·L-1 when the activation rate was 90%and FT and LT were 35.43±4.12 s and 59.98±4.20 s. In 135 mmol·L-1 glucose solution, FT and LT reached the peak values, which were 80.05±4.7s and 120.09±7.33 s, with a sperm activation rate of 90%. The sperm activation rate reached 90%when fructose concentration was 135 mmol·L-1, with maximum FT and LT values of 83.35±7.02 s and 112.68±9.35 s, respectively. The sperm activation rate was higher than 80%at pH 8-8.5; highest FT of 34.98±4.92 s and highest LT of 41.27± 4.93 s appeared at pH 8.5 and pH 7.5, respectively, with no significant difference with that of pH 7,8, and 9(P>0.05). Weak alkaline environment at pH 8-8.5 was suitable for lota lota sperm, and a better sperm motility was observed with glucose and fructose solutions as activation medium other than Na+, k+, and Ca2+.(2) The compound effects of three factors of Na+, glucose, and pH on Lota lota sperm motility showed that:the model of Na+, glucose, and pH effects on Lota lota sperm motility was established: Ywpc=0.331859×Na++0.267987xGlc+30.6087×pH-0.00327×(Na+)2-0.00094×(Glc)2-1.87889×(pH)2-0.00057Na+×Glc+0.001983Na+xpH-0.00115Glc×pH-145.733Through the response surface analysis with a model decision coefficient R2=98.88%. Both the first and secondary effects of Na+, glucose, and pH on the Lota lota sperm motility were significant (P<0.01). Interaction effects of Na+and glucose on Lota lota sperm motility were significant (P<0.05), while interaction effects of Na+, glucose, and pH on sperm motility was not significant (P>0.05). The best lota lota perm motility was observed when Na+and glucose were at 42.3 mmol·L-1 and 124.5 mmol L-1 and pH was at 8.1.(3)The results of the artificial insemination experiments in Lota lota with single activation solution and compound activation solution showed that:the fertilization rates of distilled water group,45 mmol·L1 NaCl group,135 mmol·L-1 glucose group, and optimized group were 35.46%,44.08%,47.32%, and 56.01%, respectively. Fertilization rates of the three groups were all higher than that of the control group. No significant difference between NaCl group and glucose group (P>0.05) was found, while the fertilization rate of optimized was significantly higher than that of the other three groups (P<0.05).The results of this study confirmed the good regulatory effects of the six factors such as Na+, K+, Ca2+ glucose, fructose, and pH on Lota lota sperm motility. All the separate and comprehensive regulatory effects of these factors could be well applied to the artificial insemination in Lota lota. The above conclusion provided an important basis for the reproduction theory for cold water fish. |
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