Research

Frogs are a highly diverse group that exhibit a wide variety of activity periods, ecologies, life history characteristics, and behaviors. These factors are known to influence the evolution of visual systems in other vertebrates, but have not been well studied in frogs. This project aims to characterize spectral, genetic, and morphological diversification of the visual system in frogs as it relates to these major transitions. This is a joint NSF-NERC funded project led by Matthew Fujita (UT Arlington), Rayna Bell (NMNH), and Jeff Streicher (NHM).

Most studies of the molecular evolution of vision focus solely on the visual opsins, but there are many other proteins involved in vision that may have undergone functional adaptation. Of particular interest are the proteins involved in the phototransduction cascade (the process of transforming a light stimulus into an electrical signal that can be sent to the brain). This process involves over 35 proteins and how these proteins have evolved and adapted in different organisms is largely unknown. Snakes and geckos are excellent systems to study the evolution of these proteins due to the frequent transitions between activity patterns (e.g., diurnality and nocturnality) and retinal compositions that have occurred in these groups.

In order to maintain vision across the range of natural light levels vertebrates typically utilize a duplex retina that contains rod photoreceptors for dim-light vision and cone photoreceptors for bright-light vision. Snakes and geckos, however, have a predominance of simplex retinas that contain only one of these photoreceptor types. Simplex retinas can evolve either through the loss of one photoreceptor type or through evolutionary transitions between types, termed photoreceptor transmutations. The goal of this research is to determine the contribution of these two pathways to the evolution of different simplex retinas, as well as to uncover the molecular and functional changes that accompany theses transitions.