EEB382 mclennan lec 2.pdf

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University of Toronto St. George
Ecology & Evolutionary Biology
Deborah Mc Lennan

EEB382 Lecture 2- D. McClennan November 2, 2012 Today: Function of colour (pattern..some fish may not actually see colour) How not to be seen: - flat fish: can change pattern very quickly - melanin: melanophores get filled up with pigment, deeper in skin= innervation which cause pigment to expand/contract quickly thus movement of melanin changes colour pattern of fish - flounder: pattern of spots and blotches - match the background spectral radiance(?) (background matches) - eyed flounder: can change colour very quickly-changes body in seconds - can match background pattern, even subtle details via vision Why? - The two that roughly match (flounder): water murky, a lot of green space light-donʼt need to match water well because canʼt see them as easily - The one that matches well (eyed flounder): water clear - flounder matches gravel Eye bars- bar that covers the eye - masks the eye (not entirely sure) - i.e. gobi some eye bars yellow, doesnʼt mask, whats the function?- donʼt know Counter shading- dark on top, silvery-light on sides & the bottom i.e. pelage fish i.e. “they do it with mirrors” - guanine reflects the light in such a way that makes you invisible how it works: (a) ->(~)-> (arrow looks exactly the same coming through, arrow represents light) (~)= fish ->= light (b) look down on fish, donʼt see them, camouflaged due to dark shading from above (c) look up on fish, see light coming at you from atmosphere into water, thus if below fish, canʼt see it...BUT look up at fish, itʼs still blocking the light and causes a silhouette...thus fish will always look up (which is why predators hunt from below) How to not be seen below: - herring/stickleback: torpedo shaped, thin bodies, thus small silhouette against a bright background Counter illumination - produce your own light - on belly, has row of light producing cells or photophores to reduce silhouette - i.e. lantern fish= not uniform (splotchy pattern) uneven - i.e. velvet belly lantern shark= uniform even EEB382 Lecture 2- D. McClennan November 2, 2012 - more disruptive colouration - Problem with counter illumination - i.e. cookie cutter shark- all you see is black dot, tuna goes after dot b/c it looks like what it eats...and shark bites out of tuna - Actual evidence: i.e. midshipman fish - photophores on belly - measure production of light from photophores (see graph A in notebook) - not perfect because light always changing in ecosystem - took juveniles without or with pigment they needed - dropped adult in there, in twilight conditions (thatʼs when adults come up to feed) - twice as many fish that canʼt produce counter illumination were eaten - thus counter illumination DOES produce some anti-predator protection - Functions of colour/patterns continued - a lot of this is primarily related to reproduction - i.e. males will assume bright colour pattern for attract a mate - i.e. three spined sticklebacks: spawn in streams/rivers - counter shaded fish associated with ocean habitats (silver on side, dark dorsally) - splotches on body, essentially the same as the background - male turns red orange colour during breeding (ventro-lateral surface of fish) with blue eyes - theyʼve 4 cones in eyes: UV (purple), short (blue), medium (green), long (orange/yellow) - dominant pigment matches background, thus anything else they see will be dark against background - match orange yellow pigment - females have a change in vision- sensitive to orange/red wavelengths, even if canʼt see orange/red, thus background looks dark and male looks light - this doesnʼt occur in males (thus not for male-male aggression/competition) - sex-specific change in pigments that result in this colour pattern - thus cohesive system between change in pigment and change in function in breeding - Motivational state: “I am a sexually active male”, especially since melanophores are under direct nervous control - blanching “excitement pallor”- frightened: adrenaline rush and melanin in deeper layers contracts - also “Iʼm submissive” - i.e. tilapia: lines vs dots, lines “Iʼm submissive”, dots “Iʼm aggressive” - lateral display (looks at side of fish) - (if territorial male comes across a “dotted”, agressive male):frontal display (turn on him, flare uperculum), tailbeat (mouth open, tail beating), charge, bite EEB382 Lecture 2- D. McClennan November 2, 2012 - i.e. round batfish: juveniles are called “leaf---” during day, float around on current - when 2 juveniles bump together, dominant one forms a bar-like pattern, dominant bites and then they swim away - an anti-aggrevation...but no real explanation for this (Too many will attract attention from predators) - Sophisticated Motivational Signals - stickleback males, uses glue and makes nest - develops a tiny bit of red: “not ready to nest” if nest incomplete - red male, blue eyes: “Iʼm ready to spawn” - females lay eggs in nest - then male responsible for eggs/ fryes - red signal at jaw: “Iʼm aggressive, territorial, donʼt come into nest” RE test: - wonʼt ask details on specific examples: what are the functions of counter illumination, or what are 2 problems of counter illumination? - Ultraviolet light - travels far in ecosystems - damaging - photopigment (UV) - (1)mating systems - i.e. amarillo: lives in shallow, brightly lit streams in mexico - raises fins, (space light clear) - female attracted to fins, and if female approaches, male folds fins in (reduces attraction physically) - reflective strip reflects UV light may be reason for male tucking away - rubbed gel over place where attracting UV light - sheʼs more attracted to male that has UV light (sex specific) - (2) faces: flower in UV light (reveals nectar/pollen to p
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