| A new variant of Chinese mitten crab(Eriocheir sinensis) named “River & Sea 21” was successfully bred by Shanghai Ocean University and other cooperation units in 2015. It has characteristics of high survival rate, fast growth and stable genetic traits. In this paper, “River & Sea 21” was used to investigate production characteristics, growth dynamic, gene expression and their correlation with water quality indexes in Chinese mitten crab. The results were presented as follows:Part 1. The effect of p H on the molting, growth and related gene expression of juvenile Chinese mitten crabIn order to investigate the effect of p H on the molting, growth and expression of related genes(MIH, Ec R, RXR, IGF2) in juvenile Chinese mitten crab, the “River & Sea 21” with the average weight of 0.43 ± 0.09 g was cultured in the indoor closets with four experimental group of p H=7, 8, 9 and 10(no water grass) and one control group(water grass) for one intermolting period(37 days). The results indicated that the survival rate and weight gain in the control group were significantly higher than those in the experimental groups(P < 0.05) and there were significant positive correlation between the weight gain rate and survival rate(r = 0.729, P < 0.01), while the lowest survival rate and weight gain were observed in the p H 10 group. The quantitative real-time PCR showed there were significant expression difference(P < 0.05) in MIH, Ec R and RXR genes among the different water p H groups, however, no significant expression difference(P > 0.05) in IGF2 gene. Correlation analysis showed that there were significant positive correlation between the each other of Ec R、RXR and IGF2 genes(r = 0.654 ~ 0.868, P < 0.01), indicating synergistic effects in expression in the three genes. Combining survival rate, weight gain and gene expression, it would have been concluded that the optimal p H was 8 ~ 9 for juvenile crab.Part 2. Study on relationship between growth dynamic and water quality indexes for juvenile Chinese mitten crabIn order to further investigate the growth characteristics and their relationship with water quality indexes(WQI) in rearing pond for juvenile Chinese mitten crab, this study described the growth dynamics(body weight, carapace length and carapace width at each 15 days interval) of the juvenile “River & Sea 21” reared at the Shanghai Fudao Aquaculture Professional Cooperatives. Meanwhile, this study investigated some water quality indexes(WQI), namely water temperature, dissolved oxygen, p H value and ammonia nitrogen at each 3 days interval, during the experimental period of June 18 to October 18 in 2015. The results showed:(1) There were the same growth dynamics for the three growth traits and significant positive correlation(P<0.01) between each other with coefficient of variation from 10% to 50% for body weight and from 0.50 to 0.65 for condition factor. Male crab displayed significantly growth rate than female crab since middle of October.(2) The average value of each WQI changes smoothly in each measurement cycle with water temperature at 23-32 ℃, dissolved oxygen more than 7 mg/L(periodic hypoxia phenomena existed at some special times), p H at 7.8-8.8 and ammonia nitrogen 1 mg/L.(3) Correlation analysis showed that WQI has no significant correlation with growth traits. Combining growth dynamics and WQI, it was suggested that the high temperature period(July-August) would be an important stage for growth in juvenile crab. Although there were no significantly correlation between the WQI and growth traits, it is important to pay close attention to the changes of WQI and avoid the appearance of periodic hypoxia in aquaculture of Chinese mitten crab.Part 3. Study on relationship between growth dynamic and water quality indexes for adult Chinese mitten crabIn order to further investigate the growth characteristics and their relationship with water quality indexes(WQI) in rearing pond for adult Chinese mitten crab, this study described the growth dynamics(body weight, carapace length, carapace width and body height at each one month interval) of the adult “River & Sea 21” reared at the Shanghai Fudao Aquaculture Professional Cooperatives. Meanwhile, this study investigated some water quality indexes(WQI), namely water temperature, dissolved oxygen, p H value and ammonia nitrogen at each 3 days interval, during the experimental period of February 20 to October 20 in 2015. The results showed:(1) There were the same growth dynamics for the four growth traits and significant positive correlation(P<0.01) between the each other. The crab exhibited fast growth characteristics during April to July as well as August to October, and relatively slow growth characteristics during July to August. Male crab displayed significantly growth rate than female crab since July.(2) The average value of each WQI changes smoothly in each measurement cycle or month with water temperature at 24-32 ℃, dissolved oxygen more than 8 mg/L(periodic hypoxia phenomena existed at some special times), p H at 7.7-9.1 and ammonia nitrogen 1.5-0.4 mg/L.(3) Correlation analysis showed that WQI has no significant correlation with growth traits. Combining growth dynamics and WQI, it was suggested that the high temperature period(July-August) and last molting period are two important stages for adult crab growth, and effective management would be conducted during the two stages. |
PDF Full Text Request