A closer look at pupil diversity and evolution in frogs and toads

CERVINO, N.G.; ELIAS-COSTA, A.J.; PEREYRA, M.O.; FAIVOVICH, J.

PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON. SERIES B: BIOLOGICAL SCIENCES.

ROYAL SOC

Año: 2021 vol. 288 p. 1 - 9

0962-8452

The eyes of frogs and toads (Anura) are among their most fascinating features. Although several pupil shapes have been described, the diversity, evolution, and functional role of the pupil in anurans have received little attention. Studying photographs of more than 3200 species, we surveyed pupil diversity, described their morphological variation, tested correlation with adult habits and diel activity, and discussed major evolutionary patterns considering iris anatomy and visual ecology. Our results indicated that the pupil in anurans is a highly plastic structure, with seven main pupil shapes that evolved at least 116 times during the history of the group. We found no significant correlation between pupil shape, adult habits, and diel activity, with the exception of the circular pupil and aquatic habits. The vertical pupil arose at least in the most recent common ancestor of anurans, and this morphology is present in most early-diverging anuran clades. Subsequently, a horizontal pupil, a very uncommon shape in vertebrates, evolved in most neobatrachian frogs. This shape evolved into most other known pupil shapes, but it persisted in a large number of species with diverse life histories, habits and diel activity patterns, demonstrating the remarkable functional and ecological versatility of this pupil in anurans.