Meeting Abstract
Eyes are reduced or lost across many species, representing most of the major animal lineages that have eyes capable of spatial resolution. Eye reduction and loss are generally associated with the decreased, or completely absent, levels of light associated with particular lifestyles (e.g. fossorial, parasitic) or habitats (e.g. deep-sea, subterranean). Because of the repeated occurrence across animal diversity, I consider whether there are commonalities in the proximate and ultimate processes leading to eye reduction and loss across species related to light level, habitat, or lifestyle. To attempt to address this question, I have surveyed literature on species with reduced or absent eyes in order to compare the anatomical and molecular underpinnings, as well as considered available RNAseq data to compare patterns in how both morphology and the expression of phototransduction molecules change towards a synthetic view of pattern and process in animal eye loss. Based on initial surveys, reduced light environments can lead to either reduced or expanded eyes, with commonality across species in the reduction of the numbers of expressed opsin genes, which code for the proteins involved in light detection. In contrast, habitats with no light seem to harbor animals where tissues still express opsins, albeit at reduced levels, despite the loss of the anatomical structures (e.g. photoreceptors, lens, neural pathways) required for vision. In both dim and no-light habitats, animals commonly express opsins associated with photoreceptors that are no longer present.
