Meeting Abstract
P1.101 Monday, Jan. 4 Optical characteristics of the facial pit of 4 pitviper species from different habitats BAKKEN, G.S.*; COLAYORI, S.E.; DUONG, , T; Indiana State University; Indiana State University; Indiana University School of Medicine gbakken@indstate.edu
The facial pit of pitvipers is a flask-shaped cavity divided into two chambers by a membrane covered with warm receptors. Both the pinhole camera-like anatomy and neurophysiological studies indicate a thermal imaging function. While neural image reconstruction may improve the final image, geometry indicates that the temperature contrast images formed on the membrane by thermal radiation have poor angular resolution. Thus, there is considerable uncertainty as to what a snake can ‘see’ with this organ. Here we report membrane-temperature-contrast images of typical laboratory and outdoor scenes computed by applying first-principle optical and heat transfer models to the facial pit anatomy of 4 pitviper species, Trimereseurus albolabis (typical habitat moist tropical forest and bamboo), Crotalus atrox (arid grassland and scrub), C. o. oreganus (dry woodland), and C. horridus atricaudatus (temprate deciduous forest). Our results show that optical spread functions (the distribution of radiation from a source point over the image plane) vary greatly over the pit membrane and among species. This presents a challenge to neural image reconstruction. The nature of interspecific variation suggests facial pit anatomy might be functionally related to ecological factors. Our images indicate published behavioral observations are best explained by assuming membrane receptors are significantly more sensitive than is commonly believed. Our results also show that if body and average environmental temperatures differ significantly, background membrane temperature variation may exceed the reported dynamic range of the sensory endings. Thus, the facial pit system presents many challenges that may lead to significant advances in sensory physiology and perhaps new approaches to computational image reconstruction.
