Soft-shelled Turtle Sex Differentiation And Incubation Temperature Relationship

There are two theories to account for reptiles sex determination: chromosome dependent sex determination (genetic type) and environment dependent sex determination, the latter one is that the sex of offspring depends on environmental factors and not on the chromosome. The environmental factors include density, water content, pH and so on. Incubation temperature is the most important factor. For this type of animal, sex determination during embryonic development depends on the incubation temperature of environment, which refers to as temperature-dependent sex determination (temperature dependent sex determination, TSD). In this paper, we study the incubation temperature which control sex differentiation of Trionyx sinensis by using statistical methods. At the same time we determine the sensitive period of sex differentiation by conversing experimental conditions, especially the incubation temperature. It shows as following:1. The female rate is highest, up to 96% at 24℃, and the lowest male rate is 12% at 32℃, with the much higher male rate. At (29±0.5)℃, the male and female sexual approximate 1:1. The rate of females decreased step by step with the incubation temperature increasing from 24 to 32℃, and there was a linear correlation between female rate and the incubation temperature, thus the regression equation is Y = 373.1247-11.235X.2. There is a sensitive period in Sex determination of Trionyx sinensiss. Sensitive period is determined by conversing incubation conditions (temperature). Effective temperature approximate 7100℃·h with the beginning of the gonadal differentiation at 33℃, approximately 10300℃·h with the end of gonadal differentiation. This condition of incubation result in gonad development for spermary. At 33℃, when effective temperature is 7100℃·h, we transferred the conditions of incubation to 24℃, and returned back to 32℃when effective temperature is 13000℃·h. This conversing condition of incubation result in gonad development for ovarian. At 33℃incubated for 10d, then transferred to 24℃for 10d, the last time is under the conditions of 33℃to hatched, and the female rate is highest, up 88.9%, female gonadal differentiation period K is about 6000 (13000-7100)℃·h. At 33℃incubated for 13d, K approximately 10296℃·h and then to 24℃, the male rate is up to 86.5%. It said that male gonad differentiation is end, and the K of the male gonads differentiation stage is approximately 3200 (10296-7100)℃·h. It is 2800℃·h less than female gonad differentiation.3. In this paper, the the main environmental factors were discussed, which impact on the growth and development of Trionyx sinensis. The factors consist of substrate type, substrate moisture content and incubation temperature. The experimental results show that the most appropriate substrate is hybrid substrate (coarse : general: petty =1 : 4 : 1), it is conducive to moisture and ventilation; and substrate moisture content is from 4% to 24%, and the most appropriate humidity is 4-6%. The role of incubation temperature can affect the performance of the young trionyx sinensis in the sex ratio, length of incubation period and hatching rate. The acceptive incubation temperature is from 24℃to 33℃. Incubation temperatures high, the proportion of males is high under the condition of temperatures from 24 to 33℃and the female rate was linear with temperature. At the same time the hatching rate is closely related to incubation temperature, and hatching rate increase step by step with temperature changing from 24 to 30℃. At 30℃, the incubation rate is the maximum, up to 100%.Incubation temperature and embryonic metabolism is closely related too, under high temperature metabolism will accelerate, but with low temperature the metabolism tends to slow, so the growth of embryos depends on the incubation temperature, and this can be tested from the relationship of incubation temperature and period: at 24℃for 68 days and at 28℃for 52 days, and at 33℃period shortened to 37 days.However, Trionyx sinensis eggs hatched under the incubation temperature, the period is short because yolk absorption is not complete, with young body slightly stronger;and at low-temperature, the yolk absorption is complete, the young stronger.4. The Trionyx sinensis embryonic development process, the occurrence of major organs such as kidney are researched at this paper morphologically and histologically. The corresponding results present scientific standards to accurately understand embryonic development stages and to identify determine the sex of Trionyx sinensis.