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, 102:42 | Cite as

Why is the tongue of blue-tongued skinks blue? Reflectance of lingual surface and its consequences for visual perception by conspecifics and predators

  • Andran Abramjan
  • Anna Bauerová
  • Barbora Somerová
  • Daniel Frynta
Original Paper

Abstract

Blue-tongued skinks of the genus Tiliqua (Scincidae) are characterized by their large blue melanin-pigmented tongues, often displayed during open-mouth threats, when the animal feels endangered. It is not clear whether this unusual coloration is a direct anti-predation adaptation or it may rather serve intraspecific communication, as ultraviolet-blue color is a frequent visual signal in a number of lizard species. We used spectrophotometry and visual modeling to compare blue tongues of Tiliqua gigas with tongues and skin coloration of other lizard species, and to examine their appearance through the eyes of both the conspecifics and avian predators. Our results show that (1) the tongue coloration is probably not substantially influenced by the amount of melanin in the skin, (2) lingual and oral tissues are UV-reflective in general, with blue colored tongues having chromatic qualities similar to UV-blue skin patches of other lizard species, (3) UV-blue tongues are more conspicuous than pink tongues, especially in the visual model of conspecifics. We hypothesize that blue tongues may possibly serve as a semantic (honest) signal analogous to UV-blue skin patches of other lizard species due to greater UV-bias in the vision of diurnal lizards. Regarding the social behavior and high aggressiveness in Tiliqua and their relatives, such signal might serve, e.g., in intraspecific long-distance communication between conspecifics in order to avoid aggression, and its anti-predation effect may only be a secondary function (exaptation).

Keywords

Coloration Signaling Lizards Evolution Tiliqua 

Notes

Acknowledgements

We thank Leo Fleishman for kindly providing photoreceptor data for P. broadleyi, Tomáš Grim and Dan Hanley for lending the spectrophotometer, Veronika Holáňová (Hříbalová) and Tomáš Protiva for providing C. zebrata and C. gerrardii. The work was supported by Grant Agency of Charles University in Prague (project No. 754213).

Ethical standards

This study was allowed by Ethical Committee of the Charles University in Prague, Czech Republic and approved by Ethical Committee of Ministry of Education, Youth and Sports, license no. 26582/2012-30.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Andran Abramjan
    • 1
  • Anna Bauerová
    • 1
  • Barbora Somerová
    • 1
  • Daniel Frynta
    • 1
  1. 1.Department of Zoology, Faculty of ScienceCharles University in PraguePraha 2Czech Republic

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