INTEGBI 175LF Lecture 25: 25 - Snakes II
14 May 2018
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●Locomotion:
○Lateral undulation : standard mode
■Pressure waves from head to tail
■Surface irregularities serve as pivot points
■Scutes have dif orientations
○Concertina : low-friction surfaces
■tunnels/climbing
■Posterior body is anchored, anterior stretched forward
○Rectilinear : by large-bodied, walk on ribs (rattlers, boas, pythons)
■Body in straight line
■Lit ventral scales, adjust forward, pulled down and back
■Friction with substrate causes body to move forward
○Sidewinding : low-friction, shiting surfaces (sand vipers)
■Sections of body alternatively lited, moved forward, set down
■2 sections placed in static friction - force is vertical
■Track proportional to length
●Chemoreception :
○Used in foraging and communication
○Pheromones are important
●Hearing:
○Not well-developed - no ext/middle ears
○Detect substrate/airborne sound
●Vision:
○Not developed in fossorial
○Remnant features:
■No oil droplets in cells
■No scleral ossicles
■No ciliary muscles
■Focus by moving lens forward and backward rather than accomodation (shape
change)
■Spectacle and lens contribute equally to focus - like fish
■Spectacle has blood vessels in it
■Can’t modulate amt of light w/ melanin like lizards can
■Optic tectum : where non-mammals (lizards) process visual images
■alamus : where snakes process visual images
●IR detection:
○Evolved multiple times:
■Boidae: labial pit
■Pythonidae
■Viperidae: single pit btw eye and nostril
○in, highly innervated membrane for precise detection of distance and direction
○Cool head when excited, (0.003 deg C) precise
Document Summary
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