• first located structures in 1678
• function not understood

• classic work
• blinded cat sharks- turned away from rusty pipe, didnt notice glass
• sharks respond to electrical currents

• catshark detects flounder thats burried
• blocked pores- couldnt find prey
• sharks can detect prey at close range
• may also be used for navigation

• subdermal cannals
• on head and snout- shakrs
• head and pectoral fins- rays

• pore on skin- leads to jelly pit
• group of sensory nerve cells at bottom of ampullae- alveoli
• lacks hair cells
• adapted to detect eletrical signals
• jelly similar to conductive jelly
• nerves stimulated and message sent to brain
  

• active sharks- 1500 or more
• sluggish/benthic- few hundred
• hammer heads- use like metal detector
• electrical sense is stonger when close to prey

• differnt morphology and organization
• thicked epidermis
• increased transcutaneous electric resistance
• size of ampullae greatly reduced

• detects earth magnetic field
• scalloped hammer heads: seasonally aggregate around seamounts in gulf of california
• tracked daily routes; correlated with patterns of magnetic anaomoly

• increased visual field
• increased olfaction
• increased surface area for lateral line and ampullae of lorenzini
• prey handling
• *largest relative brain size to body size

why such a large brain?

honing capabilities during feeding