| The behavior of fish is the result of adaptive evolution to environmental conditions during the long-term evolution,and is accompanied by changes in the morphological structure of body organs.At the same time,it affects their habitat environment through bioturbation.Although distant hybridization of fish has been widely used,and many hybrids with heterosis have been obtained,the changes in morphology and behavior caused by hybridization,and the relationship between morphology and behavior are rarely studied,and the ecological effects of behavior changes have not yet been effectivly evaluated.The hybridization of Misgurnus anguillicaudatus and Paramisgurnus dabryanus has been intensively carried out in China.At present,hybrids are widely bred,but the ecological effects of hybrids are still unclear.In order to accurately understand the changes in morphology and behavior of hybrid loach,the relationship between morphology and behavior,and the ecological effects caused by behavior changes.Cross-crossing and self-breeding of M.anguillicaudatus and P.dabryanus were carried out in this study and 4 seed generations were obtained,respectively M.anguillicaudatus（♀）×M.anguillicaudatus（♂）（M）,P.dabryanus（♀）×P.dabryanus（♂）（TW）,M.anguillicaudatus（♀）×P.dabryanus（♂）（MTW）and P.dabryanus（♀）×M.anguillicaudatus（♂）（TWM）.This study consists of two parts:outdoor breeding and indoor modeling.The main results and conclusions are as follows:（1）Comparison of morphological differences between hybrid progeny and inbred progenyThe traditional morphological parameters and truss parameters of the females and males of the hybrid and inbred progeny were collected respectively,and their morphological differences were analyzed by multivariate analysis.Cluster analysis results of female showed that MTW♀and TWM♀clustered together first,and then clustered with M♀,while TW♀formed an outer branch separately.The clustering results of male were consistent with the female.This indicated that,in morphologically,the two hybrid offspring were closer to the M and relatively different from the TW.The discriminatory analysis of females and males of hybrid progeny and inbred progeny were implemented separately,the results indicated that the accuracy of M♀and TW♀were 100%;the accuracy of MTW♀was 96.7%;the accuracy of TWM♀was 86.7%.The accuracy rate of M♂and TW♂discrimination is 100%;the accuracy rate of MTW♂discrimination is 90%;the accuracy rate of TWM♂group discrimination is 76.7%,respectively.On the whole,the discrimination accuracy of the parent female and male populations reached 100%,and the female and male discrimination accuracy of the two hybrid populations was lower than that of the parent,which may be due to the similar traits of the two hybrid populations.Principal component analysis was used to transform 32 traits of four female populations into 6 main factors.The 6 main factors contained more than 81.36%of the information of all traits,and the first 3 contained 62.17%.The results showed that in the four female groups,principal component 1 is mainly the truss traits,principal component 2 is mainly the head and tail traits,and principal component 3 is mainly the head and back traits.In the four male populations,principal component 1 is mainly the truss traits,principal component 2 is mainly back and tail traits,and principal component 3 is mainly head and tail traits.In general,the morphological differences between hybrid progeny and inbred progeny mainly focus on head length,snout length,body width,caudal peduncle length,posterior end of occipital bone to dorsal fin,and anal fin base end to end of caudal stalk dorsal.（2）Skeleton comparison between hybrid progeny and inbred progenyBoth the skeleton of hybrid progeny and inbred progeny are composed of brain,pharyngeal skull,spine,abdominal ribs,medullary arch ossicles,vein arch ossicles and appendage bones.The comparison results showed that the bone morphology and structure of the hybrid progeny and the inbred progeny were the same and were not affected by gender.Only the number of vertebral bones,abdominal ribs,medullary arch ossicles,vessel arch ossicles,and intermuscular bones were different.The number of vertebrae of M,TW,MTW and TWM were 41.7±1.51,43.33±1.29,42.47±1.59 and 43.1±1.35,respectively;the average number of abdominal ribs were 21.93±1.15,23±0.63,22.4±0.85 and 22.5±0.8,respectively;the total number of interstitial bones were 123.97±5.41,130.3±6.11,122±6.34 and125.6±5.97,respectively.Correlation analysis results showed that the number of abdominal ribs,the number of medullary arch ossicles,spine bones and the total number of intermuscular bones were significantly positively correlated with the number of vertebral bones（P<0.01）.This indicated that the number of vertebrae,abdominal ribs,medullary arch ossicles,pulse arch ossicles and total intermuscular bones of the hybrid progeny are between those of the parents.（3）Comparison of catch rate,survival rate,average weight and cave density under pond culture conditionsHybrid progeny and inbred progeny are placed in ponds with similar environments for breeding.The results showed that the catch rates of M,TW,MTW and TWM were28.37±3.28%,72.58±4.22%,49.89±2.87%,and 61.37±5.53%,respectively;the average tail weights were 3.18±0.33 g,13.34±3.69 g,6.32 g respectively±1.51 g and 6.54±1.35 g,respectively;survival rates were 5.46±2.34%,1.69±1.02%,11.27±1.12%,and 16.00±2.33%（calculated based on the initial number of larvae）;the density of the caves is ranked as follows:M（21.87±2.57 pcs/m2）>MTW（19.17±2.07 pcs/m2）>TWM（14.21±2.23pcs/m2）>TW（6.87±2.46 pcs/m2）.（4）Comparison of burrowing behavior and bioturbation effects in laboratoryAfter rearing in ponds was completed,hybrid progeny and inbred progeny with the same specifications were selected to observe their burrowing behavior and bioturbation effects in the laboratory（the observation device is mainly composed of circular plastic basins,sediments and overlying water）.The observation period was 360 h.The results showed that the burrowing rate of the M population was the highest under laboratory conditions,increased to 86.67%120 h after the start of the experiment,then slowly decreased and fluctuating,and maintained between 70%-80%by the end of the experiment;the burrowing rate of the MTW population increased to 68.33%at 96 hours after the start of the experiment,and then fluctuated between 50%and 70%;the burrowing rate of the TWM population reached a peak at 288 hours after the start of the experiment,showed a continuous upward trend with large fluctuations;the burrowing rate of the TW population was the lowest,reached to 26.66%at 120 h after the start of the experiment,and then fluctuating at a lower level as a whole.Tukey test showed that the burrowing rate of the four seed generations was extremely significantly different at most time points（P<0.01）.The DO of the overlying water of the experimental group dropped sharply at the initial stage,and then the downward trend slowed down and gradually stabilized;the conductivity rose sharply at the beginning of the experiment and reached a peak value,decreased slightly in the middle of the experiment,and showed a slow upward trend at the end of the experiment.p H change trend was basically consistent with the change trend of DO.The turbidity of the overlying water rose sharply at the beginning of the experiment and reached a peak,then slowly decreased and finally stabilized.These results indicated that the introduction of loach caused a drastic change in the physical and chemical properties of the sediment and overlying water in the experimental unit.After the bioturbation,the sediment surface of each group showed obvious differences.The surface of the sediments of the M group presents many caves and grooves caused by the process of burrowing;the caves and grooves of the TW group were few;the MTW group and TWM group were in the middle.After the experiment,the relative concentration of the tracers on the surface of the control group was not significantly different from that of the middle and lower layers,ranging from 0.35-0.40,with no obvious peak.Compared with the control group,the relative concentration peak of the M group and the MTW group appeared at a depth of 3 cm.At this depth,the relative concentration of the M group was 0.98 and MTW group was 0.72,and M group was significantly higher than that of the MTW group.The relative concentration peak of the TWM group appeared at a depth of 2.5 cm,which was 0.64,and the TW group appeared at a depth of 2 cm,which was 0.47.It is calculated that the vertical mobility of the tracers in the M group is the highest,which was（2.09±0.11）×10-5 g-1.cm-2.d-1.The TW group was the lowest,which was（1.58±0.13）×10-5 g-1.cm-2.d-1.The vertical mobility of tracers in the MTW and TWM in the hybrid progeny was between the two inbred progeny,respectively（1.79±0.18）×10-5 g-1.cm-2.d-1 and（1.90±0.22）×10-5g-1.cm-2.d-1.The above results indicated that the bioturbation in the M group is the strongest,followed by the MTW and TWM groups,and the TW group is the lowest.（5）Correlation analysis of morphology and burrowing behaviorCorrelation analysis of burrowing behavior and body size and bones of each group found that the correlation between burrowing rate and TL/SL was significant,also the correlation between tracers migration rate and CPD/SL,L4-7/SL,L4-8/SL,L6-7/SL,L6-8/SL,L9-10/SL and the number of vertebral bones.Based on this,it was speculated that the high burrowing rate of M.anguillicaudatus was closely related to the slender morphology and the number of fewer vertebrae;while the P.dabryanus was just the opposite;the hybrid integrates these traits of the parents to a certain extent.This study compared the morphology,skeletal,burrowing behavior and bioturbation effects of the hybrid progeny and inbred progeny of M.anguillicaudatus and P.dabryanus,showed that artificial distant hybridization may cause the hybrid progeny appear significantly different from their parents Traits and behaviors,which in turn may have different effects on the environment than their parents. |
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