Research On The Otolith Morphology And The Variance Of Saurogobio Dabryi In Jialing River

Morphological characteristics are the results of long-term interaction between organisms and living environments,and it has become one of the hot topics in modern biology research to analyze the variations of organisms morphology in different environments and explore the interrelationships between them.Otolith were the important structures to control the auditory sense and balance of fish,its morphology was closely related to heredity,environments and biological factors(age,sex),and the morphology of fish otolith often with an adaptive change in different environments.Saurogobio dabryi is an important small economic freshwater fish of Jialing River,which widely distributed in various sections.In the past,the research on the S.dabryi was mainly focused on gonadal development,sexual dimorphism and intestinal morphology,etc.At present,the study on otolith were mainly focused on marine fish,the reports of freshwater fish otolith were limited to age discrimination and species identification,while there is little research on the otolith morphology of S.dabryi.In this paper,we selected the S.dabryi asteriscus and lapillus of Jialing River as the research materials,and carried out the preliminary study on the otolith morphological characteristics and analysed the otolith morphology variations of S.dabryi in different age groups,sex and sections with traditional methods and landmark methods.Moreover,we explored the influences of different factors on otolith morphology and discussed the adaptation of otolith morphology to the environments.The results of the study are as follows:1.otolith morphology of S.dabryi: We study the otolith morphology of S.dabryi in the middle reaches of Jialing River,the main finding were:(1)The lapillus of S.dabryi was boat-shape or reniform with a smooth surface and only a rounded aragonite crystal in ventral side.The length of lapillus is 1.29 mm,the height is 1.04 mm,and the length is 1.24 times higher than the height(1.04~1.41).(2)The asteriscus of S.dabryi was round or oval with a rough surface and the number of knobs was less than 10.The length of asteriscus is 1.48 mm,the height is 1.32 mm,and the length is 1.12 times higher than the height(0.98~1.35).the antirostrum was more developed than rostrum,but the central protrusion was not very obvious,the sulcus was teardrop-shaped.(3)The results of correlation analysis showed that the oerall length,body length,forke length and the pectoral fin length were strongly correlated with the otolith,and in the correlation analysis with lapillus,the correlation between pectoral fin and lapillus was strongest.The correlation between head length and otolith was strongest in three head traits.Among the three tail characters,the caudal peduncle depth had the strongest correlation with otolith.Among the four indexes of otolith,the correlation between the asteriscus length and the external morphological parameters of the S.dabryi was the strongest.2.the otolith morphological difference of different age groups S.dabryi in the midstream of Jialing River: Through the study on the S.dabryi otolith morphology in the three age groups,we founded that the value of measured 10 parameters of otoliths were increased from age one to age three.The differences among the three age groups were mainly expressed in the aspect ratio,ellipticity,and the angle of the rostrum and antirostrum from the center of asteriscus.there was no significant difference between age one and age two,but a significant difference in age three.Age three otolith of S.dabryi has an oval shape,while the age one and two is closer to the circle.This may be related to the different growth rates of different areas of otoliths in different age stages.The subsequent principal component analysis and discriminant analysis cannot separate the otoliths from the three age groups.3.the otolith sexual dimorphism of S.dabryi in the midstream of Jialing River: Through the study on the otolith morphology of male and female S.dabryi,we founded that the value of measured 10 parameters of otoliths were female larger than male.The otolith differences between the sexes may be related to the individual growth difference between male and female.In this study,the female S.dabryi was larger than the male,which was consistent with the relationship between male and female otolith.The results of two-factor variance analysis showed that the roundness,rectangularity and the ratio of rostrum and antirostrum were significantly different between the male and female.The otolith of female has an oval shape,while the male is closer to the circle.However,the principal component analysis and discriminant analysis cannot separate male and female S.dabryi otolith.4.the otolith morphological difference of S.dabryi in different sections of Jialing River: We studied the otolith morphology of S.dabryi in the different reaches of Jialing River,the main finding were:(1)The change tendency of lapillus aspect ratio and ellipticity is that upstream was larger than downstream but smaller than midstream,while the rectangularity of lapillus was increased from upstream to downstream,besides,the roundness,format-factor and circularity of lapillus change is that midstream is the largest,upstream is the smallest.In addition to the aspect ratio and ellipticity,the average value of the other morphological features of the three sections reached a significant difference.(2)Relative warp principal component analysis divided S.dabryi asteriscus of three sections into two types,Type ? and Type ?.Type?contains the upstream of Jialing River S.dabryi asteriscus samples,while Type ? includes the middle and lower reaches of Jialing River S.dabryi asteriscus samples.Comprehensive results of traditional morphological method and landmark method showed the morphological differences of the two types were mainly reflected in the overall contour,the knob number,the basal leaf(landmark 6,7),the sulcus(landmark 10,11,12)and the widest point of ventral side(landmark 8).For example,Type?(upstream)asteriscus contour was closer to the oval,with more knobs,the rostrum angle deviation from the otolith center was smaller,the sulcus was narrower,the widest point of ventral was higher,while Type ?(midstream and downstream)asteriscus tended to be rounded,with fewer knobs,the rostrum angle deviation from the otolith center was larger,the sulcus was wider,the widest point of ventral was lower.Discriminant analysis results showed that the correct classification could reach 95.5% between two types.