ACTIVE SENSING
Lecture 7:
Energy-emitting Active Sensing Systems
ELECTRIC FISH
Energy-emitting active sensing
Geometry
M. E. Nelsonֶ M. A. MacIver J Comp Physiol A (2006) 192: 573–586
Energy-emitting active sensing
Frequency and duration ranges
M. E. Nelsonֶ M. A. MacIver J Comp Physiol A (2006) 192: 573–586
Energy-emitting active sensing
detection range
Bat (detecting musquitoes)
Dolphin (typical prey)
Electric fish (daphnia)
M. E. Nelsonֶ M. A. MacIver J Comp Physiol A (2006) 192: 573–586
Rat (contact range)
Black ghost knifefish
(Apteronotus albifrons)
The prey:
Daphnia signal characteristics
Mechanosensory
stimuli
Daphnia
Low-frequency
bioelectric fields
Perturbations to the
fish’s high-frequency
electric field
1 mm
Mechanosensory
Jerky propulsion using main antennae
 Fast power stroke – Daphnia moves up
 Slow recover phase – Daphnia sinks

Normal swimming 1-3 antennal beats s-1
 Escape bursts up to 23 beats s-1

Typical flows near antennae ~ 10 mm s-1
Kirk, K.L. 1985.
Bioelectric fields (low freq)
Daphnia produce two kinds of bioelectric
fields


Orientation dependent: up to 1000 mV,
Movement dependent: 10-100 mV, 3-15 Hz
W. Wojtenek, L. Wilkens, et al.
Bioelectric fields (low freq)
Orientation
dependent
W. Wojtenek, L. Wilkens, et al.
Bioelectric fields (low freq)
Movement
dependent
W. Wojtenek, L. Wilkens, et al.
Daphnia signal characteristics
Mechanosensory
stimuli
Daphnia
Low-frequency
bioelectric fields
1 mm
The duck-billed platypus
uses passive electro and mechano reception to
localize prey
Electro and mechano receptors
mechano
Distribution of electroreceptors (red) and mechanoreceptors (blue)
on the dorsum of the platypus bill
There are 40,000 electroreceptors and 60,000 mechanoreceptors summed over
all srurfaces of the bill
Daphnia signal characteristics
Mechanosensory
stimuli
Daphnia
Low-frequency
bioelectric fields
Perturbations to the
fish’s high-frequency
electric field
1 mm
Electric Field Generation
Power Considerations
Weakly electric fish devote about 1% of basal
metabolic rate to EOD production
Pulse fish



discharge intermittently
higher power per EOD pulse
lower duty cycle
Wave fish



discharge continuously
lower power per EOD cycle
100% duty cycle
M. E. Nelson
Self-generated Electric Field
isopotential lines (peak, in microvolts)
M. E. Nelson
Self-generated Electric Field
current flows perpendicular to the isopotential lines
M. E. Nelson
Principles of active electrolocation
Principle of active electrolocation
M. E. Nelson
Electroreceptors
~15,000 tuberous electroreceptor organs
1 nerve fiber per electroreceptor organ
mechano
Black ghost knifefish
Fabrizio Gabbiani, Nat Neurosci 2003
Prey-capture video analysis
Prey capture behavior
Simulation
Simulation
Prey capture kinematics
Longitudinal velocity
acceleration
Distance to closest
point on body surface
Electric Field Generation
Electric Organ Design
M. E. Nelson
Electric Field Generation
Electric Organ Design
• an electrocyte is a modified muscle cell, that lacks the ability to
contract and is specialized for the generation of electric current.
Electric Field Generation
Electric Organ Design
• The electric organ contains columns of stacked electrocytes
•
To generate a signal, the brain sends an electric signal to the first electrocyte
in the column, which depolarizes the innervated electroplate surface. This creates a
a depolarization wave along the electroplate column.
• Essentially, the stacked electroplates act as a series of batteries. The charge
generated from these connected "batteries" is released into the surrounding water.
Electric Field Generation
Proprioception & electroreception
manual touch
vibrissal touch
electrolocation
• body proprioception
• body proprioception
• body proprioception
• sensor’s muscle
• sensor’s muscle
• sensor’s muscle
proprioception
proprioception
proprioception
• mechanoreception
• mechanoreception
• electrooreception
• mechano-
• efference copy
proprioception
Electric Field Generation
Proprioception & electroreception
at least two types of electroreceptors:
P-type – respond to the intensity of electrical
current
T-type - respond to the phase of electrical
current
T-type are analogous to the Whisking cells in
rats, but they ARE affected by external
modulations
Complications with
emitted-energy active sensing
conspicuousness

Detection of energy by prey and predators
confusion with peers
Adaptations specific to
emitted-energy active sensing
conspicuousness

- technology war
Detection of energy by prey and predators
confusion with peers
- ciphering
- jamming avoidance
Technology war
make the probe less conspicuous to the prey/predator.
Example:
echolocating killer whales A  dolphins
echolocating killer whales B  fish
Dolphins can detect the ecolocating signals
Fish cannot
echolocating killer whales A use irregular short clicks
echolocating killer whales B use continuous emission
Technology war
make the probe less conspicuous to the prey/predator.
Example 2:
The prevalence of passive vision systems make it difficult for
bioluminescence-based active photoreception to be a
viable strategy in most ecological niches.
Solution 1: Flaslight fish open and close a “lid” to expose
their light organ briefly
Solution 2: In deep sea, vision is usually based on the
blue-green portion of the spectrum. deep-sea dragonfish
have two bioluminescent organs, one of which produces a
near infrared wavelength of light that only they can see.
Ciphering
keep a private signal that allows decoding the echo
Example: CF-FM echolocating bats
1st harmonic is weak and does not reach the peers
2nd harmonic is loud and also echoed well
pairing of 2nd harmonic (source) & delayed 2nd harmonic
(echo) would include peer calls
These bats have evolved cells that respond to
1st harmonic & delayed 2nd harmonic
other ciphering tricks?
Jamming avoidance
Jamming avoidance
Masashi Kawasaki Current Opinion in Neurobiology 1997, 7:473-479
Jamming avoidance
WALTER METZNER, The Journal of Experimental Biology 202, 1365–1375 (1999)
Adaptations specific to
emitted-energy active sensing
conspicuousness

- technology war
Detection of energy by prey and predators
confusion with peers
- ciphering
- jamming avoidance
ACTIVE SENSING
Lecture 7:
Energy-emitting Active Sensing Systems
End of lecture 7
ELECTRIC FISH