| The effects of shelter areas,differet bio-diets and light color on rowth performance and body color of the red shell Chinese mitten crab were studied in the present work in order to sheld light on the research of mechanism for body color formation and adjustment in crustacean.The main results are as follows:1.The effects of size of shields named as 0,1,2,and 4 group,respectively,on feeding and growth performance of three populations（red color,normal color and a combination of the different color crabs）were studied.The results showed that the survival rate of the red shell crabs was higher than that of the other two groups,with group 4 at 70.80%,which was significantly higher than that of other crabs（P<0.05）.For nomal color crab,the maximiun survival rate was 45.30%in group 0,and there was no significant difference among all the groups（P>0.05）.The maximium survival rate was was 62.5%in the group 4 for the mixed group,which was significantly different compared with other groups（P<0.05）.The maximium molting rate of the red shell crab was 87.50%,which was significantly higher than that of the group 0（P<0.05）.The molting rate of the group 0 and 1in the normal shell color crab was 67%,which was significantly higher than that of the other two populations.The specific growth rates（SGR）of were the highest in the 1-fold group of red-shelled crabs,the 1-fold group of normal-shelled young crabs,and the 1-fold group of young crabs in the mixed group.However,there was no significant difference among the groups（P>0.05）.The specific weight gain rate in the0-fold group of Red-shelled young crabs was significantly higher than that in the 1-fold group（P<0.05）;the highest level in the 4-fold group was 1.27%,but there was no significant difference（P>0.05）;The specific weight gain rate of multiple groups was higher than that of other groups,and the difference was not significant（P>0.05）.The highest crippled rate was 4.4%in the red-shelled juvenile crabs in the 1-fold and 2-fold groups,and there was no significant difference among the groups（P>0.05）.The maximium disability rate was 20.80%in the normal color juvenile crabs in group 0,1 and 4（P<0.05）;The maximium disability rate was 42.2%in group 4 in the mixed population,with no significant difference with other groups（P<0.05）.The maximium feeding rate of the red color crabs was 9.40%in the group 2,which was significantly higher than that in the group 0（P<0.05）.The maxium feeding rate of normal colore crabs was 11.21%in the group 1,which was significantly higher than that of the group 4（P<0.05）.The maximium feeding rate was 10.00%in the mixed group crabs,which was significantly higher than that in the group 0（P<0.05）.The maximium conversion rate of the red color juvenile crabs was 19.17%in the group 0,which was significantly higher than that in the2-fold group（P<0.05）.The highest in the 4-fold group of normal shell-colored crabs was 18.34%,which was significantly higher than that in the 1-fold group.The food conversion rate in the 4-fold group was 18.24%,which was significantly higher than that in the 1-fold group（P<0.05）.Under single-cultivation conditions,the survival rate of red-shelled juvenile crabs was higher than that of normal color population.The specific weight gain rates and specific growth rates of cephalothorax were lower than normal colore crab,but no significant difference was found（P>0.05）.2.The effects of feed Myriophyllum spicatum L,Liza haematocheila and Palaemonetes sinensis,on the body cocor and growth performance in the two shell color carbs were studied.The results showed that the survival rate of the red color crab was 80%in the fed fish group,and 53.33%of the normal colore crabs in the fed shrimp fed group,a significant difference was existed between the two groups（P<0.05）.The highest clam shelling rate was 100%in the grass and shrimp groups,and the lowest was 50%in the normal shell color of the fish group（P<0.05）.The specific weight gain rate of the red-shelled crab was the highest at 2.70%/d in the feeding group,and the lowest was 0.81%.d-1 in the normal shell-fishing group of the feeding group.There was a significant difference between the two groups（P<0.05）.The specific growth rate of shrimp head larvae fed with the shrimp group was the highest1.25%/d,and that of the normal larvae fed with grass group was 0.72%.The difference between the two groups was significant（P<0.05）.The H value of the red-shelled crab was the highest,which was 17.57°,and that of the fed shrimp was 9.50°.The difference between the two groups was significant（P<0.05）.The highest S value of the red-shelled crab was 3.43%.The lowest level of red-shelled crab was 19.69%in the fed shrimp group（P<0.05）.The highest B value of the normal shell crab was 46.21°in the castration group and 8.5°in the fish group.There was a significant difference between the two groups（P<0.05）.3.Five light colors of red,green,yellow,white,and blue were used when the light intensity was 1800±50 Lx.The effects of light with different colors on the feeding,growth and body color of two kinds of shelled color crabs were studied.The results showed that both of Chinese mitten juvenile crabs showed the various growth performance under colorful lights.The green light was benefit for juvenile crabs with the red shell to promote growth and decrease cannibalism,whereas the yellow light is benefit for juvenile crabs with the normal shell.Special growth rate of body weight and disability rate were prone to affect performance under colorful lights.In red and green light groups,the molting rate of red color juvenile crabs was significantly higher than those of other groups（P<0.05）.Except for blue light group,the cannibalism rate of normal color juvenile crabs were higher than those of red shell eras under colorful lights（P<0.05）.The Special growth rate of body weight（1.69%/d）and special growth rate of carapace length（0.69%/d）of red color juvenile crabs in green light were maximum,while those of red color juvenile crabs in red light were minimum（1.40%/d,0.39%/d,respectively）,which indicating that juvenile crabs were not suitable for growth in red light.Furthermore,ratio of food intake at daytime was observed higher than that of night time,despite of non-significant difference（P<0.05）.which suggesting that juvenile crabs showed the circadian and feeding rhythms.The feed intake and feed conversion efficiency of red color juvenile crabs was not affected significantly by colorful lights（P<0.05）.However,food intake and food conversion were inhibited for the normal color juvenile crabs under blue light,and their food intake and food conversion were promoted under yellow light.In contrast to the pre-molting shell,the value of H for the red,green,and yellow lights of the red shell juvenile crab was decreased,and the red color of bod color were deepened;while the H values of the white light and blue light groups was increased,and those were lightened;the value of S and B for each group was decreased,the shell color was lightened and blackened.However,the degree of body color was shown to be inverse.Apart from the increase in the B value under red and yellow light,body color became brighter,the S value of the crabs in each light group were decreased,the body color became lighter.Therefore,red color juvenile crabs were suitable for growth and development under green light,and their body color were deepened;normal color juvenile crabs were suitable for growth and development under yellow light,and their body color were deepened in green light.These data might provide the reference for the breeding of crabs on the selection of color light. |
