Meeting Abstract

38.4  Monday, Jan. 5  Optics of an alternative imaging system, the facial pits of Pitvipers (Viperidae: Crotalinae) COLAYORI, Samantha E*; BAKKEN, George S.; Indiana State University, Terre Haute gbakken@indstate.edu

Facial pits are specialized organs possessed by pitvipers (Viperidae: Crotalinae) that detect emitted thermal radiation. Optically, they apparently function like a pinhole camera eye. The image is formed by differential thermal radiation heating of a temperature-sensitive membrane suspended within the facial pit. The first step in understanding the image available to inform the snake’s behavior is to define the optical properties of the pit, and then use optical parameters to construct simulated images of thermographs recorded in natural and artificial conditions. The fundamental imaging property of an optical system is the spread function, which is the distribution of radiation from a point source over the image detector. The geometry of the facial pit is such that the spread function is different for source points at different azimuth and elevation angles relative to the snake. We determined spread functions for several crotalid species (including Crotalus atrox, C. horridus atricaudatus, and C. oreganus). We first constructed geometric models from serial x-ray CT sections of fresh (frozen and thawed once) specimens. We placed markers on the reconstructed pit membrane and determined the azimuth and elevation for the point source that would place each marker in the center of the spread function. We then defined spread functions for each azimuth and elevation over a 160 horizontal and 60 vertical range centered on the axis of the head. We noted significant interspecific differences in spread functions and field of view, as well as considerable variation in spread function over the field of view. We will present spread function maps and images reconstructed using the actual spread function arrays appropriate to each of the study species.