Studies On Physio-Ecological Characteristic Of Sperm Of Chinese Sturgeon, Acipenser Sinensis Gray

The Chinese sturgeon, Acipenser sinensis Gray, a typical anadromous fish, mainly lives inthe continent shelf of the East sea, Yellow sea in China, and spawns in the Yangtze andthe Pearl Rivers. However, with the construction of Gezhouba Dam in 1981, the spawningcolonies were obstructed at the middle and lower reaches of Yangtze River. Even thoughcommercial fishing of Chinese sturgeon has been prohibited and artificial propagation hasbeen carried out since 1983, the natural spawning colony resource has been declining. In1988, the fish was put in the list as a state protected animal in classâ… . At present, greatprogress has been made in the fields of morphology, reproductive biology and, especially,reproductive ecology and stock assessment of the spawning population. Yet, there waslittle knowledge of physio-ecological characteristic of sperm. The basic characteristic ofmilt, the short-term storage of milt in vitro, the ions composition of seminal plasma, andthe effects of some environment factors on sperm motility were studied from 2005 to2006. The main results are as follows:1. The sperm density of Chinese sturgeon was from 1.48×10⁹ to 5.04×10⁹ ind./mL, withthe average of 3.26×10⁹ ind./mL, the concentration of sperm was from 9.4% to 25.12%,with the average of 17.37 %, the milt are alkalescence, and the pH value was between 7.5and 8.5; the fast-movement time, total-movement time and lifetime of sperm after beingdiluted with freshwater were 76s, 114s and 162s, respectively; the milt had 2 kinds ofcolors, ivory-white and white, the ivory-white one was thicker than the white one.2. Sperm motility declined with time extending during short-term storage in vitro. Hightemperature had negative effect on milt storage, only 3 days under 20℃, but over 10 daysunder 2℃. However, the time for short-term storage of milt is so short, long-term storageneeds cryopreservation in liquid nitrogen.3. The ions composition of seminal plasma of Chinese sturgeon include Na⁺, K⁺, Ca²⁺,Mg²⁺, Cu²⁺, Zn²⁺, Cl^-, Na⁺ was the main ions, then was K⁺, Cl^-, Mg²⁺, Ca²⁺, Cu²⁺, Zn²⁺;there were significant difference in the concentration of Na⁺, K⁺, Cl^- between 2 maleChinese sturgeon (p＜0.01), but no significant difference in Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺(p＞0.05).4. The effects of environmental factors on sperm motility parameters in Chinesesturgeon including pH, cations, monosaccharide as well as osmolality were studied. Thebest pH value for activation of spermatozoa was pH 8.0. The highest sperm motility wasobserved in solutions containing 25mmol/L Na⁺, 0.3mmol/L K⁺, 5mmol/L Ca²⁺, 5mmol/LMg²⁺, 50mmol/L glucose, and with an osmolality of 50 mOsm/L, respectively. Thepresent study provides us with some basic knowledge about biosensitivity of Chinesesturgeon spermatozoa to ionic and osmolality. A sensitivity of sperm was observed afterinduction of activation of sperm motility in solution containing cations, glucose orsucrose with high osmolality. Concentrations more than 50mmol/L Na⁺, more than 0.5mmol/L K⁺, more than 10mmol/L Ca²⁺, more than 10mmol/L Mg²⁺ and osmolality morethan 75 mOsm/L had negative effects on sperm motility. Also, more than 1 mmol/L K⁺ and osmolality more than 125 mOsm/L had an inhibitory effect. More than 10 mmol/LCa²⁺ and Mg²⁺ could induce congregating reaction.5. Na⁺, Ca²⁺, Mg²⁺ were antagonistic with the inhibitory effect of K⁺ on sperm motility.This reversed effect varied with the concentration. And divalent ions were moreeffectively. And the effect of Ca²⁺ was better than that of Mg²⁺.6. The inhibitory role of high osmolality of the swiming medium (more than 100mOsm/L) and insufficient osmolality of the seminal plasma to inhibit semen motilitysuggested that osmolality is not the principal factor preventing sperm motility in seminalfluid, but K⁺ is a major inhibitory factor effecting sperm motility in seminal plasma.In conclusion, we suggested that the artificial propagation fertilization diluent shouldbe at pH 8.0, osmolity at about 50 mOsm/L, the concentration of K⁺ should be less than0.5 mmol/L K⁺, and that of Ca²⁺ and Mg²⁺ should be less than 5mmol/L.