Retinal Ganglion Counts in invasive Iguana iguana

Abstract

Introduction Iguana iguana is an emerging invasive species in southeastern North America. To better understand their ability to outcompete native species for local resources, we investigate retina ganglion cell density in order to begin characterization visual acuity potential. Materials and Methods: We obtained four specimens from wildlife veterinarians culling invasive iguanas from southern Florida. Postmortem, we conducted whole globe enucleation, with special consideration to record globe orientation within the orbit. We performed retinal wholemounts and stained retinae for retinal ganglion cells with cresyl violet acetate. We photographed the retina at 100X and counted retinal ganglion cells in randomly generated areas using Image J. Cell counts were verified by three independent and blinded investigators. We generated a cell retina showing retinal ganglion cell density across the retina, indicating the position of the fovea. Results By combining the orientation of the retina within the globe and orbit and the map of retinal ganglion cell density, our results show a single macula and fovea that is located nasally approximately one optic disc diameter anterior to the optic disc, indicating that Iguana iguana has the highest visual acuity in the temporal visual field. Conclusion Retinal ganglion cell counts in Iguana iguana indicate a highly visual animal with good visual acuity. This may help us understand their success as an invasive species.