Sexual dimorphism and skull size and shape in the highly specialized snake species, Aipysurus eydouxii (Elapidae: Hydrophiinae)

Bartosz Borczyk; Łukasz Paśko; Jan Kusznierz; Stanisław Bury

doi:10.7717/peerj.11311

Sexual dimorphism and skull size and shape in the highly specialized snake species, Aipysurus eydouxii (Elapidae: Hydrophiinae)

PeerJ. 2021 Apr 20:9:e11311. doi: 10.7717/peerj.11311. eCollection 2021.

Authors

Bartosz Borczyk¹, Łukasz Paśko¹, Jan Kusznierz¹, Stanisław Bury²

Affiliations

¹ Department of Evolutionary Biology and Conservation of Vertebrates, University of Wroclaw, Wrocław, Poland.
² Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland.

Abstract

Background: 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, Aipysurus eydouxii, by analysing two complementary features: body size and skull morphology.

Methods: We used data on body length, weight, and skull shape from 27 measurements of 116 males and females of A. eydouxii. We investigated both sexual dimorphism and allometric (multivariate and bi-variate) properties of skull growth in the analysed data set.

Results: 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.

Discussion: We suggest that the feeding specialisation in A. eydouxii 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.

Keywords: Allometry; Feeding niche; Foraging; Sexual dimorphism; Skull; Specialization.

Grants and funding

This work was supported by intramural grant from University of Wroclaw no. 1076/S/IBS/2017. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.