Borczyk Bartosz, Paśko Łukasz, Kusznierz Jan, Bury Stanisław
Department of Evolutionary Biology and Conservation of Vertebrates, University of Wroclaw, Wrocław, Poland.
Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland.
PeerJ. 2021 Apr 20;9:e11311. doi: 10.7717/peerj.11311. eCollection 2021.
Snakes exhibit sexual dimorphism in both head size and shape. Such differences are often attributed to different reproductive roles and feeding habits. We aim to investigate how sexual dimorphism is displayed in the highly specialised fish-egg-eating snake, , by analysing two complementary features: body size and skull morphology.
We used data on body length, weight, and skull shape from 27 measurements of 116 males and females of . We investigated both sexual dimorphism and allometric (multivariate and bi-variate) properties of skull growth in the analysed data set.
We found that although there was female-biased sexual size dimorphism in body length, females were not heavier than males, contrary to what is commonly observed pattern among snakes. Moreover, females tend to possess relatively smaller heads than males. However, we only found very subtle differences in skull shape reflected in nasal width, mandibular fossa, quadrate crest and quadrate length.
We suggest that the feeding specialisation in does not allow for an increase in body thickness and the size of the head above a certain threshold. Our results may be interpreted as support for prey-size divergence as a factor driving skull dimorphism since such species in which the sexes do not differ in prey size also shows very subtle or no differences in skull morphology.
蛇在头部大小和形状上表现出两性异形。这种差异通常归因于不同的繁殖角色和摄食习惯。我们旨在通过分析两个互补特征：体型和头骨形态，来研究高度特化的食鱼卵蛇如何表现出两性异形。
我们使用了116条食鱼卵蛇的雄性和雌性个体的27项测量数据，包括体长、体重和头骨形状。我们在分析的数据集中研究了两性异形以及头骨生长的异速生长（多变量和双变量）特性。
我们发现，尽管在体长上存在雌性偏向的两性体型差异，但与蛇类中常见的模式相反，雌性并不比雄性重。此外，雌性的头部往往比雄性相对较小。然而，我们仅在鼻宽、下颌窝、方骨嵴和方骨长度方面发现了头骨形状的非常细微的差异。
我们认为，食鱼卵蛇的摄食特化不允许身体厚度和头部大小超过一定阈值增加。我们的结果可以解释为支持猎物大小差异是驱动头骨两性异形的一个因素，因为在这种两性在猎物大小上没有差异的物种中，头骨形态也显示出非常细微的差异或没有差异。
