Effects Of Temperature On Reproduction, Embryonic Development And Growth Of Gobicypris Rarus

Gobicypris rarus is a member of Cypriniformes order, Cyprinidae family, Danioninae subfamily, Gobicypris genus. Gobicypris rarus is a small freshwater fish which is endemic to china. It has become a very important experimental animal because of its small size, short spawning cycle, and easy to culture.We chose36pairs healthy brood-stocks which spawning cycle are about4-6days, and distributed them to A, B, C, D, E, F six groups with different temperatures. After periods of thermal acclimate, we observed their spawning cycle, egg laying amount and egg diameter. Artificial inseminated each group, and then their fertility rate, hatching rate, deformity rate, the incubation and hatching period, the length, heart rate and survival activity index(SAI) of newly hatched larvae, larval growth and ovary development were observed and measured at5temperature groups except group F; And the results were as below:Temperature has a great influence on the reproductivity of Gobicypris rarus. group D (24±1℃) has the shortest spawning cycle and the highest once reproductive capacity. The spawning cycle would extend and once reproductive capacity decreased below or above this temperature. It has shown that the spawning of group F (33±1℃) was inhibited, only one pair spawned normally in this group. Temperature has significant effect on the egg diameter, the average egg diameter was 0.8686-0.9496mm.1. Temperature has significant effect on incubation period but not on hatching period; incubation period has negative relationship with temperature. Y=146042.925×X-2.315(Y:incubation period, X:temperature). Based on this analyze, the biological zero temperature and its effective cumulative temperature of embryonic development are13.24℃and955.81℃·h. The model of effective cumulative temperature is N=955.81/(T-13.24). From the temperature coefficients (Q10), the optimum hatching temperature for the embryonic development is27-30℃.Temperature has significant effect on fertility and hatching rates, while has little influence on deformity rate. Fertility rate and hatching rate are above90%at the temperature range of21-27℃. Embryonic death focused on blast sphere period, original bowel embryo stage, and eyes stage. It may have relationship with fertilization, organ differentiation and embryonic oxygen consumption.As the rise of temperature, the heart rate speed up, the length of newly hatched larvae increase, larvae activity slows down, and the time of half-mortality is shorten,As the rise of temperature, the length and weight of newly hatched larvae would speed up and present fluctuation change with the increasing of days. The growth rate of length faster than that of weight had the relationship with organ differentiation. As the temperature increases, the gonad development of early larval would speed up, the sex ratio also affected accordingly. High temperature leads to the increasing proportion of male Gobicypris rarus. In temperature of24±1℃(group D), the sex ratio close to1:1.The highest proportion of males in the30±1℃(group E), the ratio of female and male is1:4.17.