| Sea urchins or the rabbitfish Siganus fuscessens can control the fast growth of algae when they are co-cultured with the sea cucumber Apostichopus japonicus. Whether these two species can adapt the environment changes of the pond were not know for the mode that sea urchins cultured in the pond were rarely studied and S. fuscessens is a warm-water species. Different salinity levels were set in this study to test the high and low salinity tolerance of two sea urchins species. Acute temperature decrease and mild temperature decrease were set to detect the effect of temperature change on the hematology and serum biochemical parameters of S. guttatus. The effect of temperature on the growth and feeding of the co-cultured sea cucumber and rabbitfish were tested in addition. The results are as follows:Nine salinity levels, i.e., 41, 38, 35, 32, 29, 26, 23, 20 and 17, were set in this experiment. The sea urchin Glyptocidaris crenularis and Strongylocentrotus intermedius were respectively exposed to the nine salinity levels for experimental observation and measurement. Experimental observations were conducted at an interval of 3 hours. The activity was judged by the condition and adhering of the tube feet. The feeding status were determined by the grazing marks on the diet and by the excreted waste. Survival rate was measured by counting the surviving animals. The results show that, salinity significantly affect the survival, activity and feeding of both species of the sea urchin. The sea urchin G. crenularis died at the salinity of 41, while did not die at the salinity of 20~35. The sea urchin S. intermedius died at the salinity of 17 and 41, while did not die at the salinity of 23~35. At the salinity of 23, G. crenularis had poor activity and adhering, and feed a little, while the sea urchin had strong activity and adhering at the salinity of 26,29, 32 and 35. The sea urchin S. intermedius feed little at the salinity of 20~23, while feed while at the salinity 26~35. In summary, the optimal salinity for both G. crenularis and S. intermedius at the temperature 18.5 ℃~24 ℃ ranged 32, and the proper salinity ranged from 26 to 35 and from 26 to 35, respectively. The salinity should be controlled in the proper salinity range when the sea urchins were co-cultured with sea cucumber in the pond.Hematology and serum biochemical parameters were investigated in Siganus fuscessens(37.12±5.60) g subjected to abrupt and chronic temperature decreases. 24 ℃ was set as control with four lower temperature treatments of 20, 16, 12 and 8 ℃, sampling randomly at each designed temperature control point. The results showed that, in the acute temperature decrease treatment, red blood count(RBC), hemoglobin(HGB), platelet count(PLT) and hematocrit(Hct) in hematology decreased significantly at 8 ℃. Activities of glutamyl-transpeptidase(ALT) and alkaline phosphatase(AKP) showed a increase-decrease trend, ALT activity after below 12 ℃ was significantly higher than the control. AKP activity at 20 ℃ was significantly higher than the control. Glutamate-oxaloacetate activity were all significantly higher than the control and showed a fluctuation(P<0.05). Glucose(GLU) content in serum at 8 ℃ was significantly higher than the control, and the content at the other temperature control points was significantly lower than the control. The contents of cholesterol(CHOL), total protein(TP) and albumin(ALB) after below 20 ℃ were significantly lower than the control, triglyceride(TG) content at 20 ℃ was significantly higher than the control, and the contents at the other temperature control points were significantly lower than the control. A/G and creatinine(CREA) content at 20 ℃ were significantly higher than the control, A/G and the content at the other temperature control points had no significant difference. There is no significant difference in urea nitrogen(BUN) between the temperature control points and the control. However, in the mild temperature decrease treatment, RBC and HGB decreased significantly(P<0.05), the other hematology parameters had no significant differences. ALT activity at 12 ℃ was significantly higher than the control, AST activity at 20 and 12 ℃ was significantly higher than the control. AKP activity except at 16 ℃ was significantly higher than the control(P<0.05). GLU content increased significantly at 8 ℃, CHOL content decreased significantly at 16 and 12 ℃ compared to the control. The contents of TG, TP and CREA showed a increase-decrease trend, and the difference is that TP content could not restore to the initial level. ALB content after below 20 ℃ decreased significantly compared to the initial level. A/G at 20 ℃ increased significantly(P<0.05). There is no significant difference in BUN compared to the control(P>0.05). We suggested that the lowest growth and survival temperature for S. guttatus is 12 ℃, 8 ~ 9 ℃ is the lethal low temperature limit. If S. guttatus were selected to co-culture with sea cucumber, the water temperature should be over 12 ℃ when putting the fish into the pond, or harvested them after autumn.The S. guttatus and juvenile A. japonicus in co-culture were fed at different temperature(20 ℃、23 ℃、26 ℃、29 ℃) to investigate the effects of water temperature on growth and feeding using biochemical methods. The results showed that, the specific growth ratio(SGR) and weight gain rate(WGR) of S. guttatus and juvenile A. Japonicus significantly decreased with the increasing temperature(P<0.05). The feed rate(FR) of S. guttatus showed a downswing, the feed conversion ratio showed a increasing trend. Our results suggest that, the temperature condition, especially the highest temperature should be taken into account. The co-cultured rabbitfish in low temperature water can feed more algae and grew well to improve the culture environment and culture income. While high temperature can inhibit the feeding rate and growth of the rabbitfish so as to limit the effect of the co-culture system. |
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