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Overview
Make Strong Fields for
hunting (rare)
Make Weak fields for
other uses
(more common)
Don’t make electrical
fields, but sense them
(very common).
Electricity
for Hunting
Strongly Electric Fish
Electricity made using muscles or nerves
Torpedo
Ray
Electroplaques
Tells how many
electrons are
moving through
the circuit.
Tells how hard
the electrons are
being pushed.
12 V, 1 amp
24 V
4 X 12 = 48 V, 1 amp
1 Amp, 12 V
4 Amps, 12 V
36 V
4 Amp
Batteries 12 V and 1 Amp
Torpedo Ray
Bottom
Side!
Electroplaques
Torpedo
Ray
+- +
++
+
+
- - +
+
Stacking For Volts ; Multiple stacks for Amps
Electric Eel
6.000 electroplaques
500 volts and 1 amp = 500 watts
Overview
Make Strong Fields for
hunting (rare)
Make Weak fields for
other uses (more
common)
Don’t make electrical
fields, but sense them
(very common).
Fish that make Weak Fields
Active Electricity for
Locating prey
Avoiding predators
Navigation
Communication
Weakly Electric Fish
Mormyrids
14 Percent of all fish species = Mormyrids
Active
Sonar
Red October
“Ping”
Nimitz
Sound waves sent out by the Red October
bounce off the Nimitz and back to the Red
October. Sonar operators on the Red October
hear the reflected sound and know that the
Nimitz is there.
Active
Electrical
Senses
“gotcha”
An electrical field sent out by special
organs in the Red Fish is distorted by the
other fish. Electrical field detectors on the
Red Fish detect the distortion and know
that the other fish is there. Finds prey and
predators.
Active Electricity for
Locating prey
Avoiding predators
Navigation
Communication
Active
Electrical
Senses
Rock
Why to Electric Eels and Mormyrids
have such weird fins?
The elephant fish sets up a nice
symmetrical electrical field using it’s
electrical organ. When anything enters the
field, the field is distorted and the fish can
sense the change.
Active Electricity for
Locating prey
Avoiding predators
Navigation
Communication
Electricity for
Communication
Overview
Make Strong Fields for
hunting (rare)
Make Weak fields for
other uses (more
common)
Don’t make electrical
fields, but sense them
(very common).
Passive Electricity for
Locating prey
Avoiding predators
Navigation
Communication
All animals
make a weak
electrical field
Passive
Sonar
Red October
Sound from the engines and propeller
of the Nimitz are detected by sonar
operators on the Red October. When
they hear the sound they know the
Nimitz is there.
Passive
Electrical
Senses
An electrical field produced by normal
muscle and nerve activity in the green
fish is detected by electrical sensors on
the Red Fish.
Hammerheads and
Stingrays
Fish That Sense
Electricity: It
isn’t just for
exotic species
Ampullary Organ
for sensing electrical fields
Epidermis
Dermis
Sharks
Moving a wire through a
magnetic field produces an
electrical current
Sensors on Sharks
= Opening of Ampullae
= Lateral Line
= Canal between Ampullae
Shark Navigation
Electricity Highlights
• Some fish use muscle and nerves to make
strong fields for killing prey
• Some fish just sense electrical fields
– Passive electrical senses – detects other animals for
hunting or escape
• Other fish make weak fields for navigation or
communication
• Communication: Mormyrids zap messages to
each other and receive them
• Navigation
– Active electrical senses: zap out a field and look for
interference
• Sensors in bony fish = ampullary organs
• Sensors in sharks = conductive canals,
Ampullae of Lorenzini
The Lateral Line
Canal to
skin surface
Cupola
Hair Cells
Cupola
Hair Cells
Ampula
Crista in Ear
Lateral
Line
Canal
Neuromast in Lateral Line
Canal to
skin surface
Cupola
Hair Cells
Cupola
Hair Cells
Ampula
Crista in Ear
Lateral
Line
Canal
Neuromast in Lateral Line
Water Movement
Pore
Epidermis
Neuromasts
Dermis
Muscle
Water Movement
Water
Pore
Scale
Dermis
Muscle
Epidermis
Free
Neuromasts
Super Sensitive
No “Filter”
= Lateral Line
Pores
= Exposed
Neuromasts
Tilapia: The lateral line is
interrupted to avoid the fin
Flounder: The lateral line
goes around the fin.
Placements
avoid fins, but
also reveal the
purpose of the
Lateral Line
Schooling
Protection
Flying Fish: The lateral line is on
the bottom of the fish so that it
can sense what is beneath.
Prey Detection
Frogfish
Frog Fish: The lateral line goes
along the top of the fish so that
it can sense what is above.
Killifish
The struggling bug makes
ripples that the killifish detects
with free neuromasts
Antarctic Pagothenia
Antarctic Pagothenia
Lateral line specially tuned to
shrimp vibrations
Navigation
Blind Cavefish
Lateral Line Highlights
• Detects movements in the water
• Canal connected to surface by pores
• Movement of water detected my
neuromasts
• Neuromasts look like cristae (ears)
• Neuromasts may be exposed, but they are
extremely sensitive: not for rough water
• Lateral line and neuromasts are positioned
depending on the needs of the fish
• Lots of uses: Schooling, prey detection,
predator avoidance, navigation
Fish
Ear
Semicircular
Canals
Third canal
(horizontal) not
visible
Ampullae
Otolith
Upside Down
Fish
Hairs on hair cells straight
Right side Up
Fish
Otolith bending hairs
on hair cells
Focusing in Mammals
Lens shape changes
Near
Far
Side Views
Front View
Focusing in Fish
Muscle pulls on lens
Daytime
Cones in front
Rods Shaded
Light
Night
Rods in Front
No Shading
Cones in Back
Light
• Nose
Smell vs.
Taste?
• Mouth, & many
places
• Taste buds SCC
• Sensors in
the Olfactory
Epithelium
• Primarily for
• Many uses,
feeding
including food
location
Molecules Whooshing by in the Water
Nerves to the brain
Olfactory Epithelium
Ciliated Cells
• Amino acids: The building
blocks of protein. Some
amino acids are more
stimulatory than others.
• Steroids: Some fish are
highly sensitive to hormones
especially those related to
reproductive activities (see
below).
– Prostaglandins: Released by
female fish upon ovulation.
What Can They Taste ?
•
•
•
•
sweet, sour, bitter, salty, uma
Amino acids
Steroids: Sex hormones
Organic acids and
nucleotides:
• Carbon Dioxide: ??
• Peptide toxins: Like marine
puffer toxin
Solitary Chemoreceptor
Cells: SCC
Dispersed on external surface of
fish as well as on gills and in the
oral cavity.
These cells are sensitive to amino
acids in some species but not
others.
They are especially adept at
detecting fish mucus and some
organic acids.
• Eggs: found in a
redd
• Alevin: fry with
yolk
• Parr: Fingerlings
in fresh water,
black bars
• Smolt: Fingerling
ready for the
sea, silver
• Adult: In the sea
Does not die, returns to the sea
Homing Theories
•Imprinting: Salmon
smell the stream
•Pheromone: Salmon
smell their kin
•Which is right?
Active
Electrical
Senses
“zap”
An electrical field sent out by special organs
in the Red Fish is distorted by the other fish.
Electrical field detectors on the Red Fish
detect the distortion and know that the
other fish is there.
Passive
Electrical
Senses
An electrical field produced by normal muscle
and nerve activity in the green fish is detected
by electrical sensors on the Red Fish.
Sensors on Sharks
= Opening of Ampullae
= Lateral Line
= Canal between Ampullae