ELECTROCOMMUNICATION

By:Sharafat Ali

BS (Hons) Zoology

Electrocommunication

Electrocommunication is the communication method used by weakly electric fishes.

Weakly electric fishes are a group of animals that utilize a communicating channel that is "invisible" to most other animals: electric signaling.

Electric fishes communicate electrically by one fish generating an electric field and a second individual receiving that electric field with its electroreceptors.

Purpose of Electrocommunication

species recognition courtship and sex recognition motivational status (attack warning or

submission) and environmental conditions

Types of Electric fish Electric fish are capable of generating an

external electric fields or receive electric fields (electroreception).

Electric fish can be further divided into three categories:

strongly discharging weakly discharging fish that sense but is unable to generate

electric fields

Conti… Electric fishes generate discharge from

electric organs located near the tail region.

Electric organs are mostly derived from muscle cells (myogenic); except for one gymnotiform family has electric organ derived from neurons (neurogenic organs)

Conti… To detect the electric signals, electric

fish has two types of receptive cells Ampullary Tuberous electroreceptors

Electroreceptor organs to detect weakly electric fields, animals must possess

electroreceptors (receptive organs) that detect electric potential differences.

For electric fishes, receptive organs are groups of sensory cells rooted in epidermal pits, which look like small spots on the skin.

In each receptive organ, there are sensory cells embedded in the bottom of the opened "pit" that faces outside.

Electroreceptors detect electric signals by building up a potential difference between the outside environment and the fish body's internal environment.

Conti…

Conti… Current flow due to such potential

difference further results in a receptor potential that is presynaptic to the sensory fibers. Finally, this receptor potential leads to action potential fired by sensory cells

Phenomena of Electrocommunication

The electric organ contains electrically excitable cells called 'electrocytes', which receive simultaneous command signals from the brain to 'fire'. At the moment of 'firing', the electrocytes are asymmetrically polarized acting as serially connected batteries.

Conti…

Conti… The simultaneous firing of electrocytes results

in the electric organ discharges (EODs) which are emitted in the surrounding water. In strongly electric fishes, such as the electric eel, electric catfish, and electric rays,

The electric organ is huge containing numerous electrocytes. Therefore, their discharge voltage can reach as high as 600 volts. In weakly electric fishes, which use electricity for navigation and communication, the discharge voltage is small -- often less than a volt.

Electric organ discharges (EODs)

There are two types of EODs, pulse type wave type.

All strongly electric fishes and some weakly electric fishes are pulse-type electric fishes. They discharge short electrical pulses intermittently.

Some weakly electric fishes are wave type. They produce wave-like continuous A.C. electricity.

Conti…

Active electrolocation Electroreceptors are used to detect a

slight change of electric field cause by nearby objects. Electric fishes can thus electrically 'see' objects in an environment where vision is useless (at night, or in murky water). This process is called 'active electrolocation' because the source of electricity that they use for electrolocation is their own electric organ.

Conti…

Types of Electric Fishes Electric fishes are divided into the three

main categories Strongly electric fish

electric eel electric catfish electric rays

Conti… Weakly electric fish

knife fishes elephant nose

Fishes that can only sense electricity sharks rays skate catfish paddle fish Platypus (though not a fish, they are

electroreceptive.)