lect 5 - vision Flashcards
(23 cards)
advantageous of vision
- effective over short/mid distances
- complex signals
- influenced by ambient conditions
- instantaneous signals
trichromats
3 colour receptors
eg. humans
tetrachromats
4 colour receptors
eg. birds and reptiles
rods
black + white vision photoreceptors
- abundant in nocturnal mammals
- low spatial acuity
cones
colour vision photoreceptors
- narrow vision sensitivity
- usually abundant in the retina of colourful animals
fovea
creases in the retina that give sharp focused vision at certain distances
- not in amphibians, but some reptile
ciliary muscle
focusing at different distances
scleral ossicle
bone to keep structure in the eye
(not in snakes)
oil droplet
changes the colour receptor within the photoreceptor cell (filter/tunes)
- different # of oil droplets depending on the colour they need to see
lizard in(visible) trails
rub waxy pores against substrate to smear compounds around the environment
- compounds reflect UV
- territory marking
- invisible to mammals
diurnal lizard vision
- broad field vision (side of the head eyes)
- 2 fovea (focus close + far)
- retina is all cones
- sensitive to jerky movements
- static and dynamic visual displays
nocturnal lizard vision
eg. geckos
- large eyes proportional to head
- exclusively large cones
- no oil droplets
- pupil opens completely in 1hr
- extremely sensitive to colour in very dark conditions
parietal eye
third eye on top of the skull in lizards and tuatara
- used for tracking circadian rhythms and seasonal activity
- paired organ (1/2 pineal gland)
amphisbaenian eyes
- iris fused with ciliary bodies (can’t focus well)
- covered by head scale
- only detect light levels + shapes
- eyes not needed in totally fossorial species
snake eyes
may come from fossorial spp (lost lot of functions)
- no ciliary muscles
- no oil droplet
- no scleral ossicle
- yellow or clear lens
- most snakes only dichromatic in daylight
UV signaling in snakes
large # of nocturnal, arboreal snakes reflect large amounts of UV
diurnal snakes
- gigantic pupils + horizontal slits
- binocular vision
pit organ
contains membranes that convert heat radiation (infrared) into electrical signals,
nerve goes directly to the brain and is overlaid with signals from eye
eg. viper loreal pit had TRPA1
TRPA1
wasabi receptor protein in humans
- repurposed in snake pits to detect heat and pain from heat
tortoise vision
tetrachromats that may be able to see into the UV spectrum
amphibians vision
- eyes similar to reptiles but no fovea
- emphasis on underwater vision
- 2 type of rod photoreceptors + 2 cones = tetrachromats
- good vision in low light
diurnal
- see well in bright light
- colour vision in bright light
- tetrachromats (mostly)
nocturnal
- high sensitivity to light
- colour vision in low light
- di or trichromats
