Otolith morphology of Saurogobio dabryiand the variance in different sections of Jialing River

The purposes of this study were to understand the otolith morphology of Saurogobio dabryi in Jialing River, as well as its phenotypic consequences of water environments variations. 195 S. dabryi individuals were collected from the upper (Guangyuan section), middle (Peng’an section) and lower reaches (Hechuan section) of the Jialing River from June to July, 2016. The lapillus and asteriscus of the left side were used as the study materials. 14 morphometric parameters were measured with traditional methods and transformed into shape indices such as aspect ratio, roundness, format-factor, circularity, rectangularity, ellipticity, etc. Besides, 12 landmarks were established around the rostrum, antirostrum and sulcus of asteriscus by landmark methods. The results showed that the lapillus of S. dabryiwas reniform, the morphology had no significant difference among three sections. the asteriscus of S. dabryiwas round or oval with a rough surface, the number of knobs was less than 20, the antirostrum was more developed than rostrum, but the central protrusion was not very obvious, the sulcus was teardrop-shaped. Relative warp principal component analysis divided S. dabryi asteriscus of three sections into two types, Type Ⅰ and Type Ⅱ. Type Ⅰ Ⅰcontains the upstream of Jialing River S. dabryi asteriscus samples, while Type Ⅱ includes the middle and lower reaches of Jialing River S. dabryi asteriscus samples. The 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). The discriminant analysis results showed that the correct classification could reach 95.5% between two types. The asteriscus of S. dabryi from different river sections of Jialing River can be divided into two significantly different types, which may be related to the adaptation of environmental factors such as water temperature and flow velocity, for example, the slender Ⅰasteriscus of Type Ⅰ with more knobs could be better adapted to the changeful rapids environment at low temperature of upstream.