| Structure of Myxocyprinus asiaticus (Bleeker) spermatozoon was studied with light microscope (LM) and transmission electron microscope (TEM). The lengths of different parts of spermatozoa were measured under LM, and 31 spermatozoa were measured. Effects of 6 environmental factors on sperm motility in Myxocyprinus asiaticus(Bleeker) were studied by observing the fast moving time and total duration of the sperm. By taking the fast moving rate of spermatozoa after being motivated as the index, the effects of four preservation fluids were evaluated, using 0.7% NaCl solution as contrast.The results were as follows:The spermatozoon of Myxocyprinus asiaticus could be mainly divided into three parts: head, midpiece and tail (flagellum). Head of spermatozoon was spherical shaped under LM and horseshoe shaped under TEM when it was longitudinally sectioned. Head was mainly consisted of nucleus, without acrosome. The chromatin in nucleus was dense, nuclear vesicle could be seen in the nucleus. Nuclear membrane could clearly be seen outside of the nucleus. Only a little cytoplasm was existed in head. There was a deep implantation fossa at the caudal-central end of the nucleus, the depth of which was about 2/3 of the length of head, and held a centriolar complex. Midpiece was at the posterior end of the nucleus, and consisted of centriolar complex and sleeve. Two sides of the sleeve were almost symmetrical. The centriolar complex consisted of proximal centriole (PC) and distal centriole (DC).The angle of PC and DC was almost right, ie."T"shape like. A big space existed between the axial filament and cell membrane, and there were vesicles and cytoplasm in the big space. The tail could be divided into two parts (principal piece and end piece), and with lateral fins on both sides of the flagellum. The principal piece of the spermatozoon tail was long and possessed a conventional"9+2"structure. The light microscopy measurement showed that head length, tail length and total length were 2.56±0.14μm, 52.69±5.59μm, 55.51±5.67μm respectively.The tolerance ability to acid and base of Chinese sucker sperm was strong. The most suitable pH value for the sperm was 8, at which the fast moving time of the sperm was 40.17±7.22s, and the total duration was 1148.55±26.13s.The fast moving time was 44.55±4.83s in 102mmol/L NaCl, and it was the longest fast moving time in all concentrations of NaCl, when the concentration of NaCl was 51mmol/L, the total duration of the sperm was the longest, and was 153.96±8.79s. The most suitable KCl concentration for the sperm was 75mmol/L, at which the fast moving time was 32.10±0.68 s, the total duration was 1841.12±35.70s which was the longest among all the observed total durations. When the concentration of glucose was 100mmol/L,the fast moving time was the longest in all glucose solutions, and was 25.74±1.82s.When the glucose solution concentration was 200mmol/L,the total duration was the longest in all glucose solutions ,and was 480.07±20.03s.The most suitable concentration of CaCl2 solution for the sperm was 75.6mmol/L,at which the fast moving time was 28.40±2.34s,the total duration was 97.83±13.64s.When the concentration of MgCl2 solution was 75.6mmol/L,the fast moving time was the longest in all MgCl2 solutions ,and was 31.66±4.78s.When the concentration was 18.9mmol/L,the total duration was the longest in all MgCl2 solutions ,and was 114.51±14.01s.The results showed that it is feasible to use preservation fluids to preserve the spermatozoa of Chinese sucker under common low temperature(0～4℃). The differences among different preservative fluids were obvious. Among which ,B was the best, which could keep 80% of spermatozoa having fast moving ability within 120h, D was second to B only, which could keep 80% of spermatozoa having fast moving ability within 84h. And the fast moving time of Chinese sucker spermatozoa in fresh water was 24±3.52 s, the total duration of it in fresh water was 128±9.5 s.
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