Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

2.2 Methods & Materials
The experiment described here involved the high-magnification imaging of spectacle blood flow in
colubrid snakes and attempt to characterize the spectacle vascular dynamics under varying conditions,
including at rest, when moulting, and when a visual threat is presented.
2.2.1 Animals
The experimental subjects were 3 coachwhip snakes (Masticophis flagellum, Colubridae) obtained
from a local pet store and private keepers. They ranged in age from 2 to 5 years, with the following
sizes: 130 cm (snout to vent) & 445 g; 120 cm & 320 g; and 97 cm & 240 g. The snakes were housed
in separate terraria equipped with burrows and water dishes. Ambient temperature was kept at
approximately 25˚C with daytime basking spots of ~31˚C, and lighting was on a 12:12 h light:dark
cycle. They were fed to satiety once per week with frozen/thawed adult mice. A fourth specimen was
excluded from the experiments due to high apparent stress levels.
2.2.2 Experimental Equipment and Setup
All observations were made using a Topcon SL-5D slit lamp to which was mounted a video camcorder
(Sony HC-7) via a beam splitter. The subjects’ eyes were illuminated with a near infrared(NIR)-filtered
light source using a combination of cross- and retro-illumination. NIR was used to minimize
disturbance to the subjects, as it is not perceptible by coachwhips who lack the infrared-sensing pit
organs found in crotaline vipers and in some boas and pythons. This required modifying the slit lamp
by placing near-infrared (NIR) filters in the light path between the lamp and condenser. The filters
consisted of either exposed negative photographic film (Kodak Portra 160VC on a polyester base) or
unexposed positive film (Kodak Ektrachrome Duplicating Film on a polyester base) processed to full
density (see Figure 2-2, next page, for transmission spectra).
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