Sexual size dimorphism in the viviparous caecilian amphibian Geotrypetes seraphini seraphini (Gymnophiona: Dermophiidae) including an updated overview of sexual dimorphism in caecilian amphibians

In: Amphibia-Reptilia
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  • 1 1Institut für Zoologie, Fg. Zoologie 220a, Garbenstr. 30, Universität Hohenheim, 70593 Stuttgart, Germany
  • | 2 2Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich Schiller-Universität Jena, Erbertstrasse 1, 07743 Jena, Germany
  • | 3 3Naturhistorisches Museum, Thüringer Landesmuseum Heidecksburg, Schlossbezirk 1, 07407 Rudolstadt, Germany
  • | 4 4Abteilung Zoologie, Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
  • | 5 5Institut für Evolution und Ökologie, Vergleichende Zoologie, Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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Sexual size dimorphism (SSD) describing intersexual size differences of a given taxon is a widespread phenomenon in the animal kingdom. SSD plays a significant role in understanding life history and mating system evolution. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes an accurate comparison between sexes.

Here, the phylogenetically derived teresomatan and viviparous caecilian Geotrypetes seraphini seraphini was analysed for patterns of sexual dimorphism. In terms of body size females were the larger sex, but when body length was adjusted male-biased intersexual differences in cloacal shape appeared. The larger female size is likely explained by fecundity selection as clutch size was positively correlated to female body length. Unexpectedly a cryptic, ontogeny related variation of the nuchal collars was found. An overview of SSD in caecilians including data for 27 species of nine out of ten existing families revealed a quite high number of taxa showing sexually dimorphic head size dimensions exclusively present among phylogenetically derived teresomatan caecilians. Still further research including insights into the behavioural ecology and molecular ecology of mating systems is warranted to better understand the evolution of sexual size dimorphism of caecilian amphibians.

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