Evaluating effects of temperature, salinity, starvation and autotomy on molting success, molting interval and expression of ecdysone receptor in early juveniles of the mud crab, Scylla paramamosa in
【摘要】：Newly molted first stage juvenile crabs(C1) of the mud crab, Scylla paramamosain, were subjected to different temperature(14, 20, 26, 32 and 39°C), salinity(5, 10, 20, 30 and 40‰), starvation and autotomy(for autotomy experiment, the second stage crabs(C2) were used) to assess their effects on molting success, molting interval and corresponding expression of ecdysone receptor(Ec R) of the crabs. The results showed that at a low temperature of 14°C no molt occurred with a subdued EcR mR NA level detected. In contrast, a higher temperature of 32°C induced a significantly increased expression of Ec R gene with significantly shorten C1 molting interval as compared to other treatments. However, as temperature increased further to 39°C, the expression of Ec R gene dropped abruptly from 6 h onward and all C1 crabs died without molt. On the other hand, a low salinity of 5‰ increased Ec R mR NA levels at 72 h and shortened molting interval significantly while high salinity of 40‰ led to opposite results. No significant difference in percentage molting success was detected for salinity ranged from 10 to 40‰. When C1 crabs were subjected to starvation for longer than 48 h, the expression of Ec R was found to be significantly restrained when compared to the feeding control, and none of the starved crabs successfully molted. Meanwhile, although molting success of C2 crabs was not significantly affected by autotomy, molting interval was significantly increased from 5.8 days of intact crabs to 6.2 days for the autotomized crabs. Interestingly, the expression level of EcR gene of autotomized crabs was found initially restrained(i.e. during the first 120 h) when compared to intact crabs, but increased sharply to a level significantly higher than the control at 134 h(i.e. during premolt stage of the autotomized crabs). Our results showed that temperature, salinity, starvation and autotomy all affected molting of early juvenile mud crabs and changes of EcR mR NA level in the crabs appeared to play an important role in regulating the molting process. It also showed that S. paramamosain early juveniles could tolerate a broad range of temperature and salinity and should be cultured between 26-32°C and 10-30‰ salinity since such condition generally produced high molting success and shorter molting interval.