EEB382 Lec 3 McLennan.pdf

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Ecology & Evolutionary Biology
Deborah Mc Lennan

EEB382 Lec 3- D. McLennan November 9, 2012 Lateral Line Examples of touch: - Humans: actually touch - Cats: whiskers-pressure changes - Fish: “distant” touch (“svenning”) - lateral line: detect movements far away from them, they donʼt have to touch directly with fins or body. Can we sven? - can feel the current (i.e feel wind around us) - can feel things around it (i.e. feeling seagull beat wings above our heads) Problem posed by the environment - Abiotic: wind, waves - Biotic: yourself, (i.e. running, you move through air), prey, predators, conspecifics (others moving around you) - how do you differentiate between abiotic and biotic? Sensory Cell - responds to body movements - SENSORY HAIR CELL: involved in sensory line receptor - mechanoreceptor - KINOCILIUM- long cilia - STEREOCILIA- short cilia - recall cilia= thin extension of cell(hair-LIKE), built in structure with microtubules that can move - Tree: sensory hair cells are extremely old, atleast as old as the chordates (showed up before jawed vertebrates) - lost after amphibians (thus we donʼt have it) - lateral line placko?: two internal related systems, 1= electrosensory systems, 2= lateral line...they develop in similar areas of the fish - NEUROMAST- sensory hair cells together, stereocilia and kinocilia extend into a “glucose amino-glycan, similar to jelly-fish coating”, or jello-like covering (which is quite flexible, moveable) - Water hits cup and it moves, thus moving kinocilia, when bent they depolarize, sending impulses to the nervous system - if water moves towards kinocilia, hypopolarization - if water moves towards kinocilia through sterocilia, depolarization - intensity of firing related to degree of bending of kinocilium - i.e. 2 sets of afferent nerve fibers from hair cell to nervous system - 2 Types of Lateral Line System - (1) Superficial neuromasts (Chondrichthyes: pit organs)- sit free on body - respond to velocity of water flowing over them, detects water movement - faster the water flows, the more they fire (velocity detectors) EEB382 Lec 3- D. McLennan November 9, 2012 - responds to intensity of velocity even if static - direct contact to water - i.e. brain can be fooled b/c brain fills in information ...time lag with info entering brain..think sponge and squirrel fish - Superficial nervous system: - Function: Rheotaxis=orientation in a current (rheos- stream/ current, taxis- arrangement)...orient downwind from prey items in current to detect/capture prey - (i.e. Bald notothen, arctic fish, gylcoprotein in blooded= antifreeze)...put fish in current with different velocities - knock superficial neuromasts in lateral line temporarily with antibiotics - surgically remove superficial neuromasts or completely destroy lateral line, they lose the ability to orient - they canʼt find a way to orient themselves in the current and maintain their position in low to medium flow only...important because people thought this was due to vision only - Problem (cues): increased firing rate as water moves faster=inability to respond to subtle cues from other things such as prey items...overwhelmed by turbulent environment - Thus, where are you likely to live? - black dots are superficial neuromasts on a goldfish - they live in slow, sluggish waters, kind of muddy (vision is decreased) - below 1000m, meso-pelagic and baso-pelagic in deep waters have really developed lateral lines - ie hairy anglerfish= long extensions with superficial neuromasts - i.e. Alabama Cave fishes: eyes donʼt even start to develop
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