Meeting Abstract
As early tetrapods transitioned from life in water to life on land more than 300 million years ago, the eye underwent a remarkable evolutionary transformation. This major event in the history of vertebrates facilitated the transition to the complex optical system used by most terrestrial tetrapods today. Previous research identified that the shift to vision through air was marked by a three-fold increase in absolute eye size. This dramatic increase in eye size remained significant even after the scaling effects were accounted for. It is unknown, however, if this pattern is a general evolutionary response tied to transitions from water to air. We therefore sampled another such event, focusing on a more recent transition from life in water to partial life on land: the evolution of mudskippers. Mudskippers are a potentially paraphyletic assemblage of amphibious fish phylogenetically nested within the Gobiidae. We measured the horizontal eye diameter of preserved specimens for a total of 54 gobiid species, and accounted for body size by measuring standard length, body depth, and body weight. When plotting the species averages of eye size against body size variables, we observed that the eyes of mudskippers tended to be larger than the eyes of their close relatives. Even though the phylogenetic relationships of mudskippers and their closest relatives are currently poorly understood, it appears unlikely that our findings are biased by phylogenetic covariance. While not as dramatic as seen in early tetrapods, mudskippers tend to have relatively large eyes, suggesting that the increase of eye size may be a general evolutionary response tied to transitions from water to air.
