Morphological and skeletal comparison and ecological adaptability of Mandarin fish Siniperca chuatsi and big-eye Mandarin fish Siniperca kneri

Most of the closely related fish species are similar in appearance,with slight differences.This study evaluated 35 morphological characteristic parameters and the number,shape,and spatial location of bones in the skull and vertebrae of the mandarin fish Siniperca chuatsi and big-eye mandarin fish Siniperca kneri.We can understand their ecological adaptability,compare their morphological and skeletal differences,and elucidate the relationship between their phenotypic trait differences and skeletal characteristics.The results were as follows:1.The Student’s t-test results revealed significant differences between S.chuatsi and S.kneri in terms of head depth,head back length,snout length,interorbital distance,distance of the eyes from the oral fissure,and width between the posterior trunk and base of the caudal fin.Principal component and discriminant analysis showed that the main morphological differences between S.chuatsi and S.kneri were in the eye position,head hump and body shape.2.There was no significant difference in the number and shape of the skull and vertebrae between S.chuatsi and S.kneri,but they differed in spatial position.The terminus of the maxilla in S.chuatsi is located at the lower border of the postorbital bone,but at the anterior in S.kneri.The size of head hump is closely related to the spatial location of the splanchnocranium in S.chuatsi and S.kneri.The angles between the caudal vertebrae centrum and each of the following:the neural arch and spine;haemal arch and spine of S.chuatsi are larger than those of S.kneri.In conclusion,the morphological differences between S.chuatsi and S.kneri are closely related to the spatial position of skeleton.These phenotypic differences reflect the ecological adaptation of mandarin fish to different natural environments.