SUMMARYIn comparison with the other amphibian orders, the Anura (frogs) and Urodela (salamanders), knowledge of the visual system of the snake-like Gymnophiona (caecilians) is relatively sparse. Most caecilians are fossorial with, as far as is known any surface activity occurring mainly at night. They have relatively small, poorly developed eyes and might be expected to possess detectable changes in the spectral sensitivity of their visual pigments. Microspectrophotometry was used to determine the spectral sensitivities of the photoreceptors in three species of caecilian, Rhinatrema bivittatum, Geotrypetes seraphini and Typhlonectes natans. Only rod opsin visual pigment, which may be associated with scotopic (dim light) vision when accompanied by other 'rodspecific' components of the phototransduction cascade, was found to be present. Opsin sequences were obtained from the eyes of two species of caecilian, Ichthyophis cf. kohtaoensis and T. natans. These rod opsins were regenerated in vitro with 11-cis retinal to give pigments with spectral sensitivity peaks close to 500nm. No evidence for cone photoreception, associated with diurnal and colour vision, was detected using molecular and physiological methods. Additionally, visual pigments are shortwavelength shifted in terms of the maximum absorption of light when compared with other amphibian lineages. Supplementary material available online at

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There have been a growing number of studies into the visual evolution of vertebrates. However, there remain few detailed integrative studies on the visual system of amphibians using morphological, molecular and physiological methods outside of a few model species. There are many examples of amphibian species that are closely related phylogenetically, but occupy vastly different ecological niches and so provide a substantial resource for the study of adaptive evolution. This review will examine the published literature on the three living orders of amphibians, the Anurans, Caudata, and Gymnophiona.

Mohun, S.M. and Wilkinson, M. 2015. The eye of the caecilian Rhinatrema bivittatum (Amphibia: Gymnophiona: Rhinatrematidae). -Acta Zoologica (Stockholm) 96: 147-153.The reduction in the visual system of the Gymnophiona has been noted by many authors. Adult caecilian amphibians eyes are small, covered by skin and sometimes bone, with retinal cells that contain only rod opsins and co-option of structures usually associated with the visual system used for novel sensory structures and functions. Here, we provide a description of the eye of Rhinatrema bivittatum, the first of any rhinatrematid caecilian, and consider its significance for our understanding of the nature of the eye in the last common ancestor of living caecilians. Characters discovered include zonule fibres, an aqueous humour and the remnants of an attachment that could be a protractor lentis muscle.