A Comparative Study On Ammonia-Nitrogen Tolerance,Disease Resistance And Muscle Nutrition Of The Self-Cross And Cross F₁ Generations Of Misgurnus Anguillicaudatus And Paramisgurnus Dabryanus

Misgurnus anguillicaudatus and Paramisgurnus dabryanus are important economic fishes in China.Relatively,the P.dabryanus grows faster and is larger,while the M.anguillicaudatus has more delicious meat,market acceptance and higher prices.With the increasing market demand,it is very important for the healthy development of loach farming to breed hybrid loach species with delicious meat,strong resistance and fast growth.In order to study the hybridization of M.anguillicaudatus and P.dabryanus in ammonia nitrogen resistant ability,disease resistance and muscular nutritional effects,this study on M.anguillicaudatus,P.dabryanus selfing and hybrid,winning four seeds generation,namely the M.anguillicaudatus♀x M.anguillicaudatus came（MM）,M.anguillicaudatus♀x P.dabryanus came（MP）,P.dabryanus♀x M.anguillicaudatus came（PM）,P.dabryanus♀x P.dabryanus came（PP）,and made a series of related research,the main results were as follows:（One）Comparative study on ammonia-nitrogen tolerance of self-crossing and hybrid F₁ generation of M.anguillicaudatus and P.dabryanus.（1）The semi-lethal concentration of ammonia nitrogen of four species of loach was detected under the experimental conditions of six gradient concentrations of NH₄Cl,namely 0 mg/L（control group）、200 mg/L、400 mg/L、800 mg/L、1600 mg/L and 3200mg/L.The order from high to low lethal concentration of total ammonia of the four loachies was:MM（1212 mg/L）>PP（984 mg/L）>MP（857 mg/L）>PM（681 mg/L）,and non-ionic ammonia lethal concentration was:MM（60.39 mg/L）>PP（49.03 mg/L）>MP（42.79 mg/L）>PM（34.00 mg/L）.（2）The activities of superoxide dismutase,lysozyme and phosphatase in the muscles and liver of four species of eachfish were detected at 0 mg/L（control group）and 200 mg/L under NH₄Cl stress for 24h.In the control group,the activity of superoxide dismutase in the muscles and liver of the four species of loachies was between147.79±46.54 U/m L～203.98±10.65 U/m L and 179.95±9.27 U/m L～205.00±10.20U/m L,respectively,showing a trend of MM>PP>MP>PM with no significant difference between each group（P>0.05）.In the experimental group,the activities of superoxide dismutase（SOD）in the muscles and liver of the four species of Portia were significantly increased（P<0.05）,by 18.98%～21.36%and 3.58%～11.59%respectively.In the control group,lysozyme activity in the muscles and liver of the four species of boach was between 7.25±2.69 U/L～7.81±0.74 U/L and 7.96±0.47 U/L～8.57±0.38U/L,respectively,showing a trend of MM>PP>MP>PM with no significant difference between each group（P>0.05）.In the experimental group,lysozyme activity of the four species of botia superciliaris was significantly increased（P<0.05）by 17.34%～26.90%and 10.84%～23.80%.In the control group,the activity of phosphatase in the muscles and liver of the four species of loachies was between 31.25±4.43 IU/L～40.80±1.73 IU/L and 37.46±3.22IU/L40.32±3.56 IU/L,showing a trend of MP>PP>MM>PM with no significant difference between each group（P>0.05）.In the experimental group,the phosphatase activity of the four species of botia superciliaris was significantly increased（P<0.05）by11.42%～28.92%and 8.09%～21.03%.To sum up:under ammonia stress,all the four species of loachies can self-regulate and improve the activities of enzymes such as superoxide dismutase,lysozyme and phosphatase to improve the ammonia-nitrogen tolerance ability.The ammonia-nitrogen tolerance of MM and PP in the self-crossing group was better than that of MP and PM in the hybrid group.MP in the hybrid group was superior to that in the PM group in terms of semi-lethal dose,phosphatase activity and lysozyme activity.（Two）Comparative Study on resistance to Aeromonas Vivestris of self-crossing and hybrid F₁ generation of M.anguillicaudatus and P.dabryanus.（1）A.Vivestris is one of the important pathogens causing diseases of loach.In this study,the isolation,purification and identification of Aeromonas Vivestris from the body of the sick gold loach were conducted.（2）The semi-lethal concentrations of autocross and hybrid offspring of loach and paraplegia chinensis were determined under the concentration of 1×10⁶、1×10⁷、1×10⁸、1×10⁹、1×10¹⁰ CFU/m L.The results showed that the order of the semi-lethal dose of the four species of aeromonas auricularis was MM（3.55×10⁷ CFU/m L）≈PP（3.55×10⁷CFU/m L）>MP（1.26×10⁷ CFU/m L）>PM（7.94×10⁶ CFU/m L）.（3）The activities of superoxide dismutase,lysozyme and phosphatase in the muscles and liver of the four species of Portia superoxide were detected 24h after infection with aeromycete at 0 CFU/m L and 1×10⁶ CFU/m L（control group）.In the control group,lysozyme activity in muscle and liver of the four species of porpoise was between 8.20±0.58 U/L～8.55±0.35 U/L and 8.33±1.02 U/L～9.03±0.69 U/L.In the experimental group,lysozyme activity of the four species of botia superciliaris was significantly increased（P<0.05）,with an increase rate of 15.79%～25.45%.In the control group,the activity of superoxide dismutase in the muscles and liver of the four species of porpoise was between 175.66±8.11 U/m L and 197.97±9.63 U/m L and 178.12±9.96 U/m L and 203.09±9.73 U/m L,respectively,showing a trend of MM>PP>MP>PM with no significant difference between each group（P>0.05）.In the experimental group,SOD activity of the four species of loach was significantly increased（P<0.05）,with the increase rate ranging from 8.19%to 12.99%.In the control group,the activity of phosphatase in the muscles and liver of the four species of porcine adult fish was between 35.46±2.98 IU/L～40.08±3.22 IU/L and35.75±3.16 IU/L～39.41±3.00 IU/L,showing a trend of MP>MM>PP>PM,but there was no significant difference between each group（P>0.05）.In the experimental group,the activity of phosphatase in the muscles of the four species of botia superciliaris was significantly increased（P<0.05）,and the increase rate was 14.16%～23.0%.To sum up:all the four species of botia superoxide dismutase,lysozyme,phosphatase and other enzymes can be improved through self-regulation to improve the ability of resisting A.Vivestris under the infection of A.Vivestris.The resistance of MM and PP in the self-crossing group was better than that of MP and PM in the hybrid group.MP in the hybrid group was superior to that in the PM group in terms of semi-lethal dose,phosphatase activity and lysozyme activity.（Three）A comparative study on the muscle nutrients of self-crossing and hybrid F₁ generation of M.anguillicaudatus and P.dabryanus.The muscle nutrients,amino acids,fatty acids and other indexes of self-crossing and F₁ hybrid of four seeds were analyzed.The results showed that MP（19.22±0.56）%≈MM（19.22±0.72）%>PP（17.41±1.25）%>PM（14.81.±2.21）%was the order of the contents of crude protein in the four seeds from high to low.The proportion of essential amino acids in total amino acids from high to low is:MM（41.25%）>MP（40.76%）>PM（40.73%）>PP（40.68%）;The proportion of the total amino acids of umami flavor in the total amino acids from high to low was:MM（38.98%）>MP（38.86%）≈PP（38.86%）>PM（38.57%）.The order of the crude fat content of the four self-crossing and hybrid offspring was PM（8.11±2.43）>MP（6.50±2.12）>pp（3.62±1.12）>MM（1.02±1.54）.In addition,the contents of monounsaturated fatty acid（MUFA）,C18:3N6（-methyl linolenic acid）and C18:1N9C（methyl oleate）in the hybrid PM and MP were significantly higher than those in the self-crossbred.To sum up:the four species of botia superciliaris are rich in nutrition and a good source of protein.The hybrid progeny showed some advantages in muscle nutrition.MP was superior to MM、PP and PM in crude protein content,and PM was superior to MM、PP and MP in crude fat content.