嘉陵江不同江段蛇耳石形态特征及差异

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

  • 摘要: 为研究蛇耳石的形态特征以及不同环境下的耳石形态差异,以蛇左侧微耳石和星耳石作为研究材料,利用传统形态法测量耳石的14个参数且将其转化为11个形状指标,并利用地标点法在星耳石上选取12个地标点,对2016年6—7月间采自嘉陵江上游、中游、下游的195尾蛇的耳石样本进行形态研究。结果显示,蛇微耳石呈肾形,3个江段微耳石形态无显著差异;蛇星耳石呈圆形、椭圆形,表面粗糙,脊突数少于20,翼叶较基叶发达,中央突不明显,主凹槽轮廓似水滴状。相对扭曲主成分分析将3个江段的蛇星耳石分为两种形态类型:Ⅰ型和Ⅱ型,其中Ⅰ型主要为嘉陵江上游江段蛇的耳石样本,Ⅱ型则包括嘉陵江中游和下游的蛇耳石样本。传统形态法和地标点法的综合结果表明,两种类型耳石形态差异主要表现在整体轮廓、脊突数,以及基叶、主凹槽和背侧距离等特征上,逐步判别分析对Ⅰ型和Ⅱ型星耳石的正判率达95.5%,区分效果较好。研究表明,嘉陵江不同江段蛇星耳石分为两种类型,且存在显著的形态差异;蛇星耳石的形态差异可能是对水温、流速等环境因子主动适应的结果,如在上游生活的蛇,其较细长且脊突较多的Ⅰ型星耳石能够较好地适应上游低温、多变的急流环境。

     

    Abstract: 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.

     

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