title: Eye and pit size are inversely correlated in crotalinae: Implications for selection pressure relaxation.
abstract: Mate, prey, and predator recognition often depend on the integration of information from multiple sensory modalities including visual, auditory, and/or olfactory inputs. In Crotalinae, the eyes sense visible light while the pit organs detect infrared (IR) radiation. Previous studies indicate that there is significant overlap between the eye and pit sensory fields and that both senses are involved in recognition processes. This study investigated the relationships between eye and pit sizes in this taxonomic group as a function of phylogeny and habitat. In view of the fact that pit orientation depends largely on snout shape, pit vipers were grouped as follows: 1) arboreal, 2) terrestrial with rounded snout, and 3) terrestrial with pointed snout. The pit orientations and habitant patterns were fully independent of the Crotalinae phylogenetic tree. The phylogenetic generalized least squares model showed that both eye and pit areas were not of significantly phylogenetic relatedness, implying alternatively a strong effect of adaptation on eye and pit sizes. Negative correlations between relative eye and pit areas in terrestrial (both pointed and rounded snouts) and arboreal species were statistically significant. Our results suggest that the eyes and pits function in a complementary fashion such that selection for IR-perception relaxes selection pressures on the visual system and selection for visual discrimination relaxes selection pressures acting on the IR-system.
authors.affiliation: Department of Herpetology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Herpetology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Amphibians and Reptiles, Museum of Vertebrate Zoology, University of California, Berkeley, California.
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Papenfuss
authors.affiliation: Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Lu
authors.affiliation: Department of Herpetology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
authors.forename: Yezhong
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000818:Animals; D017753:Ecosystem; D005123:Eye / Q000033:anatomy & histology*; D010802:Phylogeny; D017819:Viperidae / Q000033:anatomy & histology*; D014796:Visual Perception
keywords: adaptation; infrared perception; phylogeny; pit character; vision