Electrosensation in weakly electric fish

Question 1

What are the two types of electric sense in fish? What does each type allow the fish to be able to do?

Answer 1

Passive (more common) and active
Passive - ability to detect electrical activity of other organisms e.g. heartbeat
Active - ability to generate their own electric field and sense things that disturb the field

Question 2

What are the different types of weakly electric fish?

Answer 2

Gymnotiformes form a wave of current
Mormyriformes form a pulse current
Evolved separately

Question 3

What are electrocytes?

Answer 3

Modified muscle cells in electric organs

Question 4

Describe electroreceptors

Answer 4

Either ampullar (detects passive electrical fields around them, low frequency) or tuberous (high frequency electric discharge receptors)
All hair cells and form part of the lateral line.

Question 5

What are the two types of tuberous receptors and what do they do?

Answer 5

Time markers have a high sensitivity and fixed latency, Used to detect timing of a fish’s electric organ discharge
Amplitude coders have low sensitivity overall but high sensitivity to changes in the fish’s electrical field

Question 6

What are the time markers and amplitude coders called in the mormyrids?

Answer 6

Time coders = K receptors

Amplitude coders = Mormyromasts

Question 7

What receptors are involved in active electrolocation?

Answer 7

Tubular

Question 8

How is the sensory information in our body perceived in the brain?

Answer 8

As a homonculus on the somatic sensory cortex

Question 9

What four things is the electric field used to detect?

Answer 9

Capacitance
Distance
Conduction
Location/movement

Question 10

Why is capacitance an important feature to detect?

Answer 10

Living organisms store charge so they can separate them from inanimate objects

Question 11

How does corollary discharge inhibition work?

Answer 11

A motor response generates a reafferent copy

Sensory receptors take this into account and modulate their responses to cancel it out

Question 12

What is the jamming avoidance signal?

Answer 12

A response to solve the problem of the summation of similar frequency EODs
The fish with the highest frequency will increase its frequency further and the fish with the lower frequency will decrease it further (Rose review)