Mechanoreception
http://upload.wikimedia.org/wikipedia/commons/8/82/Spherical_pressure_waves.gif
What is sound? How is it different in water? Two primary systems
for detecting vibrations (sound) and changes in water pressure
1.Lateral line system 2.Inner ear
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Sensory hair cell Lateral line systemvibration sensing
structure Sensory neuron Cilia Nucleus Synapse Neuromast Support
cell Nerves Cupula
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Exposed, free standing on skin or in grooves Function depends
on species/habitat Habitats with flowing water or high turbulence
Few neuromasts Habitats with still or turbid water Many neuromasts
Lateral line systemsuperficial neuromasts
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Individual/population level variability in superficial
neuromasts Natural selection acts on sensory systems to better
adapt a species to its habitat
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Shielded from large-scale water motion Better at detecting high
frequency sound Lateral line systemcanal neuromasts Epidermis Scale
Lateral line canal Lateral line pore NerveNeuromast
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Lateral line systemcanal neuromasts Anterior lateral line
systempores or canals Uses of the lateral line system?
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Lateral line systemtoadfish example
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Lateral LineElasmobranchs
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Fish have pair of inner ear structures Two chamberstop chamber
connects three semicircular canals Canals filled with fluid &
contain sensory hair cells Acceleration & direction change
Inner earfor balance
Otoliths #2-3 for hearing Lower chamber lined with sensory hair
cells Sagittabiggest otolith Inner earfor hearing 1 3 2
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Inner EarPearl fish e.g.
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Magnetic Reception Sensing the Earths magnetic field for
navigation Poorly studied in fishes Magnetite (FeO 4 ) & iron
deposits Lab studies Important for small- & large-scale
migrations
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Electric fieldsa sphere where charged particles (e -, Na +, Cl
- ) experience magnetic force Salt water great conductor Organisms
produce electric fields Cells maintain voltage across membranes
Neurons, muscle cells Field fluctuates & attenuates with
distance Electroreception What contributes most to a hiding fishs
electric field?
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Ampullary ReceptorsAmpullae of Lorenzini Arise from same
precursor cells as neuromasts Detect external sources Respond to
gradients in field strength Sense size & distance Ancestral
vertebrate characteristic Secondarily lost in Neopterygii
Secondarily evolved in some teleost groups Uses? Locations?
