|Other Abstract||The production of first batch transgenic fish marks the advent of new era for fish genetics and breeding. Transgenic fish show great advantages for application to aquaculture due to their improvement on growth rate, feed conversion efficiency, resistance to disease and extreme condition. Fish may be considered the best candidate for the first marketable transgenic animal for human consumption. However, till date, no transgenic fish have been released into natural water body for commercialized cultivation as food, some of the reasons for this are the possible ecological risk posed by transgenic fish. Hence, carefully evaluation of the ecological risks posed by transgenic fish is one of the important aspects for achieving their commercialization.
In order to evaluate their possible ecological risks, the present work primarily studied the biological traits of ‘all-fish’ growth hormone transgenic common carp (Cyprinus carpio L.) which could had great effects on their population fitness. At the same time, we used the ‘all-fish’ growth hormone transgenic common carp as a model system to explore the trade-offs between growth rate and survival, reproductive characteristics and swimming performance. The main results are presented as follows:
1. A line of fast-growing ‘all-fish’ growth hormone transgenic common carp was produced. Separating rates of the transgene in F2, F3, F4 and F5 were all 50%, examined by test cross. F2 transgenic fish had a mean body weight 1.8-2.5-fold heavier, and a mean specific growth rate (SGR) value 10%-20% higher than the controls. The results showed that ‘all-fish’ growth hormone transgene has effectively integrated, transmitted stably in Mendelian ratios in the homozygous line of transgenic common carp and could prompt the growth rate of common carp.
2. At 22.4 ± 0.09 °C, the average hatch time were significantly advanced about 2 h for transgenic carp compared to their nontransgenic siblings. There was not any significantly differences in hatch rate between the offsprings of transgenic males and control males hybrided with an control female. There were not any significantly differences in standard length and specific growth rate of standard length between transgenic fry and nontransgenic siblings at endogenous nutrition stage. At exogenous nutrition stage, transgenic fry had significantly higher body weight, specific growth rate of body weight, standard length and specific growth rate of standard length than nontransgenic siblings. In condition of artificial cultivation，transgenic fry and juvenile carp had significantly higher mortality than nontransgenic siblings. The result supported that there was a trade-off between growth rates and survival, i.e. faster-growing individuals had lower survival.
3. The mean body weight and standard length of transgenic carp were 1.3-2.2 times and 1.1-1.4 times than that of their nontransgenic siblings respectively. During the sampling period, transgenic females had significantly lower gonad index than nontransgenic sibling females. The gonad index of transgenic males was significantly lower than that of nontransgenic sibling males when spawn did not occur, but the differences were not significantly any more at the first two monthes after spawn. Transgenic fish had significantly lower or similar absolute gonad weight than their siblings. Compared to nontransgenic siblings, the gonad development of transgenic fish was significantly delayed. The present results showed the ‘all-fish’ growth hormone transgenic carp mature later, and their rapid growth was at the cost of reduced reproductive investment.
4. Transgenic carp had a mean absolute Ucrit (cm/s) value 22% or mean relative Ucrit (BL/s) value 24% lower than the controls. It suggested that fast-growing ‘all-fish’ GH-transgenic carp were inferior swimmers. It is also supported that there was a trade-off between growth rates and swimming performance, i.e. faster-growing individuals had lower critical swimming speed.
5. Principal component analysis identified differences in body shape between transgenic carp and nontransgenic controls, with transgenic fishes having significantly larger head depth, longer caudal length and smaller depth of the body and caudal region. Morphology had significant effects on swimming performance. Higher critical swimming speeds are related to the combination of deeper body, deeper caudal region and shorter caudal length. These findings suggested that morphological variations in GH-transgenic carp were responsible for their lower swimming abilities in comparison with nontransgenic controls.
6. Transgenic carp had significantly shorter cell length and width, smaller erythrocyte surface and volume, unchanged cell length – width ratio and larger cell surface – volume ratio. Transgenic fish had significantly higher routine metabolism, but their maximum metabolism was similar to controls. There were not significant differences in hematocrit, blood hemoglobin concentrations, plasma glucose, lactate, and cholesterol and protein concentrations between transgenic carp and nontransgenic controls at rest, but transgenic fish had significantly lower mean resting corpuscular hemoglobin concentrations and higher plasma triglyceride concentrations. Exhaustive exercise did not induced significant changes of hematocrit, hemoglobin concentrations and mean corpuscular hemoglobin concentrations in both strains. Plasma glucose and lactate increased significantly following exhaustive exercise and lasted for 4h. The manners of plasma glucose concentrations responding to exhaustive exercise were similar between two strains, but transgenic fish exhibited reduced response in plasma lactate concentrations compared to controls. Exhaustive exercise evoked significantly higher plasma cholesterol and triglyceride concentrations for 1h in transgenics which were not found in nontransgenic controls. Plasma protein concentrations were not altered by exhaustive exercise in transgenics but lower from 2h post-exercise in nontransgenic controls. These findings indicated that ‘all-fish’ growth hormone transgenic carp had significantly smaller erythrocyte appearance, higher routine metabolism, similar maximum metabolism, oxygen transport characteristics and changed physiological responses (plasma lactate, cholesterol, triglyceride and protein) to exhaustive exercise compared with controls.|