The Research Of Effects Of Ca²⁺ And Mg²⁺ In Seawater On The Growth And Physiology Of Juvenile Paralichthys Olivaceus

A series of indoor trials were conducted to investigate the effects and mechanism of concentrations of Ca²⁺ and Mg²⁺ on the growth, metabolism, energy budget, immune-enzyme activities, histology, and element concent of fish body and otolith in juvenile Paralichthys olivaceus at salinity of 30 by means of artifical seawater at 20℃. The primary results were listed below.1 Effects of Ca²⁺ and Mg²⁺ concentrations and Ca²⁺ concentrations in seawater on growth, metabolism and energy budget of juvenile Paralichthys olivaceus(1) The effects of Ca²⁺ and Mg²⁺ concentrations (1:3) in seawater on growth, metabolism and energy budget of juvenile P. olivaceus were investigated respectively at 20℃and salinity of 30 by means of artifical seawater. The Ca²⁺ and Mg²⁺ concentrations were set as follows, A-700, B-1100, C-1600 (control), D-2200, and E-2800 mg/L, respectively. The results of this 60 d experiment during different Ca²⁺ and Mg²⁺ concentrations indicated that survival of all treatments were over 90% and there was no significant difference on food conversion efficiencies (FCE) among different treatments (P>0.05). The specific growth rates (SGR) and food intake (FI) of all treatments decreased with increasing of the Ca²⁺ and Mg²⁺ concentrations. The energy gained from food (C), energy for growth (G), energy lost through respiration (R), energy lost through excretion (U) and energy lost through feces (F) decreased with increasing of Ca²⁺ and Mg²⁺ concentrations (P<0.05). Percentages of energy for growth (G/C), energy lost through respiration (R/C) and energy lost through excretion (U/C) were significantly affected by different concentrations of Ca²⁺ and Mg²⁺ (P<0.05), while percentage of energy lost through feces (F/C) was not significantly affected (P>0.05). At the same time, the Ca²⁺ and Mg²⁺ concentrations significantly influenced the ammonia-N excretion rates, oxygen to nitrogen, and pepsin activities (P<0.05). The ammonia-N excretion rates of all treatments decreased with increasing of Ca²⁺ and Mg²⁺ concentrations, while the opposite occurred for oxygen to nitrogen. (2) The effects of Ca²⁺ concentrations in seawater on growth, metabolism and energy budget of juvenile P. olivaceus were investigated respectively at 20℃and salinity of 30 by means of artifical seawater. The Ca²⁺ concentrations were set as A1-200, B1-400 (control), C1-800, D1-1600, and E1-3000 mg/L, respectively. The results of this 60d experiment during different Ca²⁺concentrations indicated that the survival of all treatments were over 90% and there was no significant difference on specific growth rates (SGR), food intake (FI) and food conversion efficiencies (FCE) (P>0.05). The Ca²⁺ concentrations significantly influenced energy lost through excretion (U), moisture %, crude lipid %, energy %, the percentages of energy for growth (G/C), and energy lost through excretion (U/C) (P<0.05). The Ca²⁺ concentrations significantly influenced the ammonia-N excretion rates, oxygen to nitrogen, and pepsin activities (P<0.05). However, there was no significant effect on oxygen consumption rate and lipase activities (P>0.05). The ammonia-N excretion rates of all treatmets increased with increasing of the Ca²⁺ concentrations, while the opposite occurred for oxygen to nitrogen.The results indicated that the Ca²⁺ and Mg²⁺ concentrations can affect the growth and energy budget of P. olivaceus. The SGR decreased with increasing of Ca²⁺ and Mg²⁺ concentrations. However, there was no significant effect on growth by Ca²⁺ concentrations. The Ca²⁺ and Mg²⁺ concentrations and Ca²⁺ concentrations can affect the growth of juvenile P. olivaceus through affecting the FI, FCE, energy lost through respiration (R), and energy for growth (G) at the prophase of experiment. Thus, the growth of different treatments tend to consistent at the end of the experiment.2 The effect on Ca²⁺ and Mg²⁺ concentrations and Ca²⁺ concentrations stress in seawater on SOD and CAT enzymetic activity of juvenile Paralichthys olivaceus(1) Ca²⁺ and Mg²⁺ concentrations stressThe effects of Ca²⁺ and Mg²⁺ concentrations in seawater on immune-enzyme activities of juvenile P. olivaceus were investigated at salinity of 30 by means of artifical seawater at 20℃. The Ca²⁺ and Mg²⁺ concentrations for short-term stress were set as follows, 200, 700, 1600 (seawater), 1600 (control), 2800, and 4800 mg/L, respectively while the Ca²⁺ and Mg²⁺ concnentrations for chronic stress were set as follows, 700, 1100, 1600 (control), 2200, and 2800 mg/L, respectively. In the short-term stress experiment, the results showed that there was no living fish in Ca²⁺ and Mg²⁺ concentrations (4800 mg/L) at 9 d while the survival of other treatments was 100%. The SOD activities increased temporarily and then decreased with prolonged exposure. The SOD activities of all the treatments before 24h was higher than that in the control (P<0.05). And there were steady trend on SOD activities during 2-9 days. The same trend also occured on CAT activities. In the chronic stress experiment, the survival rate of all treatments was over 90% after 60 d experiment. There was significant differences on the effect of SOD activities among these treatments (P<0.05). However, there was no significant differences on CAT activities (P>0.05). The SOD and CAT activities of treatment 2200 mg/L were high among these treatments while that of treatment 2800 mg/L were low.(2) Ca²⁺ concentrations stressThe effects of Ca²⁺ concentrations in seawater on immune-enzyme activities of juvenile P. olivaceus were investigated at salinity of 30 by means of artifical seawater at 20℃. The Ca²⁺ concentrations for short-term stress were set as follows, 50, 400 (control), 383 (sea water), 1500, 3000, and 4000 mg/L, respectively while the concnentrations for chronic stress were set as follows, 200, 400 (control), 800, 1600, and 3000 mg/L, respectively. In the short-term stress experiment, there was significant effect on both SOD and CAT activities of P. olivaceus during 9 d experiment while the survival of all treatments was 100%. The SOD activities were increased at 3-6 d. The CAT activity of treatment 50 mg/L was always higher than other treatments within 9 d, while that of treatment 1500 mg/L, 3000 mg/L and 4000 mg/L were almostly lower than that of control. In the chronic stress experiment, there was significant difference on CAT activities during 60 day's experiment, (P<0.05). However, there was no significant on SOD activities (P>0.05). Thus, the survival of all treatments was over 90%. The CAT activities of treatment 800 mg/L and treatment 3000 mg/L was significantly lower than that of treatment 200 mg/L and treatment 1600 mg/L.The results indicates that there were some effect on the SOD and CAT activities under the variation of Ca²⁺ and Mg²⁺ concentrations or Ca²⁺ concentrations. The SOD and CAT activities of different treatments were increased or restrained at the prophase of the short-term stress experiment. Some days later, the enzyme activities tended to stable. However, the enzyme activities in high ion concentrations may always be restrained under chronic stress experiment.3 The effect on Ca²⁺ and Mg²⁺ concentrations in seawater on element content of fish body and otolith of juvenile Paralichthys olivaceus(1) The effects of Ca²⁺ and Mg²⁺ concentrations (1:3) in seawater on element content of fish body and otolith of juvenile P. olivaceus were investigated at 20℃and salinity of 30 by means of artifical seawater. The Ca²⁺ and Mg²⁺ concentrations were set as follows, A-700, B-1100, C-1600 (control), D-2200, and E-2800 mg/L, respectively. The fish body contains many elements including Ca, P, Na, Mg, Sr, and so on. The P, Ca, Na and Mg content in treatment A was significantly lower than other treatments (P<0.05). The Sr content in fish body decreased with increasing of Ca²⁺ and Mg²⁺ concentrations. It was found that otolith length, otolith width, and otolith weight decreased with the ascending of Ca²⁺ and Mg²⁺ concentrations while the opposite occurred for otolith length to width (L/W). The otolith also contains many elements of which mostly in otolith decreased with increasing of Ca²⁺ and Mg²⁺ concentrations. And the same trend happened on the ratio of Sr/Ca%, Mg/Ca%, Fe/Ca% and Cu/Ca%.(2) The effects of Ca²⁺ concentrations in seawater on element content of fish body and otolith of juvenile P. olivaceus were investigated at 20℃and salinity of 30 by means of artifical seawater. The Ca²⁺ concentrations were set as A1-200, B1-400 (control), C1-800, D1-1600, and E1-3000 mg/L, respectively. Many elements also were found in fish body under Ca²⁺ concentrations experiment. The P,Na,Mg,Sr, Fe,Mn and Ni content in fish body decreased with increasing of Ca²⁺ concentrations. The Ca²⁺ concentrations significantly influenced the otolith length, otolith width, L/W and otolith weight (P<0.05). And the otolith length and width of treatment A1 was significantly lower than that of treatment B1 and treatment C1. The L/W of treatment A1 was significantly lower than that of treatment D1. And the otolith weight of treatment A1 was significantly lower than that of treatment B1 and treatment D1 (P<0.05). The Ca²⁺ concentrations significantly influenced the elements content of otolith except Na, Fe and Mn (P<0.05). The Sr content of otolith decreased with increasing of Ca²⁺ concentrations. The ratio of Sr/Ca% and Mg/Ca% also decreased with the ascending of Ca²⁺ concentrations.The results indicates that element content of fish body and otolith were significantly affected by Ca²⁺ and Mg²⁺ concentrations and Ca²⁺ concentrations. The ion concentrations can affect cumulation of element in fish body and otolith. Therefore, research on the element content of fish body and otolith plays a important role on otolith growth, cumulation of ion, and estimation of environment.4 The effect on Ca²⁺ and Mg²⁺ concentrations in seawater on histology of juvenile Paralichthys olivaceus gill and kidney(1) The effects of Ca²⁺ and Mg²⁺ concentrations (1:3) in seawater on histology of juvenile P. olivaceus gill and kidney were investigated at 20℃and salinity of 30 by means of artifical seawater. Five Ca²⁺ and Mg²⁺ concentrations were set as follows, A-700, B-1100, C-1600 (control), D-2200, and E-2800 mg/L, respectively. Histological observation indicates that Ca²⁺ and Mg²⁺ concentrations significantly influence the numbers of gill chloride cells (P<0.05). However, there is no obvious effect on microstructure of kidney among these treatments. The Ca²⁺ and Mg²⁺ concentrations significantly influence the ultramicroscopical levels of gill chloride cells. Compared to the control, the tubular network in gill chloride cells in low Ca²⁺ and Mg²⁺ concentrations treatment is developed and the numbers of mitochondria increased a little. However, the numbers of mitochondria in high Ca²⁺ and Mg²⁺ concentrations treatment is significantly less and the tubular network is looser in the gill chloride.(2) The effects of Ca²⁺ concentrations in seawater on histology of juvenile P. olivaceus gill and kidney were investigated at 20℃and salinity of 30 by means of artifical seawater. The Ca²⁺ concentrations were set as A1-200, B1-400 (control), C1-800, D1-1600, and E1-3000 mg/L, respectively. Histological observation indicates that Ca²⁺ concentrations significantly influence the numbers of gill chloride cells (P<0.05). There is no obvious effect on microstructure of kidney during the experiment. However, Ca²⁺ concentrations significantly influence the ultramicroscopical levels of gill chloride cells. Compared to the control, the tubular network in gill chloride cells in low Ca²⁺ concentrations treatment is developed and the numbers of mitochondria decreases a little while the chloride cell in the fish gill has more RER. In high Ca²⁺ concentrations treatment, the numbers of mitochondria decreased significantly and the tubular network is looser in the gill chloride while the chloride cells have low density of cell matrix.The results of histology indicates that Ca²⁺ and Mg²⁺ concentrations and Ca²⁺ concentrations significantly influence the numbers and structure of gill chloride cells. However, there is no significantly effect on the microstructure of kidney. In high ion concentrations treatment, the numbers of mitochondria was significantly less and the tubular network was looser in the gill chloride. The results showed that the unbalance of ion ratio in seawater can induce the change of organic structure of fish body.