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ELECTROGENESIS IN FISHES By ABDUR ROUF SAMIM

This document summarizes electrogenesis in fishes. It describes that electrogenesis refers to the production of electrical impulses in living organisms, observed in fishes, reptiles, and mammals. There are two types of electric fishes - strongly electric fishes like torpedo and electrophorus, and weakly electric fishes like raja and gymnotus. Electric organs are specialized organs that produce electric fields outside the body, built from electroplates embedded in connective tissue. The location of electric organs varies between species, and electric organ discharges can be monophasic, biphasic, or polyphasic pulses. Electric organs are used for food procurement, defense, communication and other functions.

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ELECTROGENESIS IN FISHES ABDUR ROUF SAMIM M.Sc.(Final) FISHERY SCIENCE AND AQUACULTURE
INTRODUCTION  Electrogenesis 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 ORGANS Name of fishes Shape of electric organ Location 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 DISCHARGES  Monophasic 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
Receptor Sensory Nerve Fibre Brain Optic Nerve Electric Organ Motor Nerve 1 2 Pathways of neural control of electric organ
FUNCTION OF ELECTRIC ORGAN  Food procurement  Defense  Species and sex recognition  Direction finding  Communication  Navigation
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.
References  www.wired.com  www.elguanche.info  www.revolvy.com  www.keywordsuggests.org  Brown, animal physiology ,2nd volume.  Notes provided by Prof. Mukhtar Ahmad Khan.
ELECTROGENESIS IN FISHES By ABDUR ROUF SAMIM