ELECTROGENESIS IN FISHES

ABDUR ROUF SAMIMM.Sc.(Final) FISHERY SCIENCE AND AQUACULTURE

INTRODUCTIONElectrogenesis refers to the production of

electrical impulses in the tissues of a living organism.

Observed in all animals such as fishes, reptiles, and mammals etc.

TYPES OY ELECTRIC FISHES Strongly electric fishes Example: Torpedo, Electrophorus etc. Weakly electric fishes Example: Raja, Gymnotus etc.

RajaElectrophorus

Electric organs are organs specialized for the production of an electric field outside the body.

Built up from a large number of disc like cells, called electroplates.

Electroplates embedded in a jelly like extracellular material and enclosed within a compartment of connective tissue.

Diagram showing electric organs

ELECTRIC ORGANS

DISTRIBUTION OF ELECTRIC ORGANSName of fishes Shape of electric

organLocation of electric organ

Torpedo Flat kidney shape On either side of mid-line

Malapterurus Lozenge-shape Located in skin

Raja (String ray) Spindle-shape Lying parallel to the spinal cord in the tail

Torpedo Raja

PATTERNS OF ELECTRIC ORGAN DISCHARGESMonophasic pulses Biphasic pulses Polyphasic pulses

KINDS OF ELECTRIC ORGAN DISCHARGE

Electrophorus: one small pulse followed by four large pulse.

Electric shark: repetition of sequence of events.

Torpedo: four large pulses which are continuously repeated.

MECHANISM OF ELECTRIC ORGAN DISCHARGE

+ + + + + + +_ _ _ _ _ _ _

+ + - - - + + + - - + + + - - -

_ _ _ _ _ _ _ + + + + + + +

Resting phase

Action Potential Spike stage

ReceptorSensory Nerve Fibre Brain Optic

Nerve

Electric OrganMotor Nerve

1

2

Pathways of neural control of electric organ

FUNCTION OF ELECTRIC ORGANFood procurement DefenseSpecies and sex recognitionDirection findingCommunicationNavigation

WHY ARE FISHES IMMUNE TO THEIR OWN ELECTRIC CURRENT ?

Got myolated nerve fibers with high degree of insulation.

Excitatory muscle fibers have high threshold of excitation.

Referenceswww.wired.comwww.elguanche.infowww.revolvy.comwww.keywordsuggests.orgBrown, animal physiology ,2nd volume.Notes provided by Prof. Mukhtar Ahmad

Khan.