Continuous Electrical Signals from the Tail of a Fish, Gymnarchus niloticus Cuv.

Abstract

THROUGH the kindness of Dr. K. R. S. Morris, Gold Coast, I received a living specimen of Gymnarchus niloticus, a fish which occurs in the rivers of West Africa and in the Nile. Observation of this fish in an aquarium has revealed two striking features: (i) a mode of locomotion through waves passing over the extended dorsal fin and executed forwards and backwards with equal ease; (ii) a marked ability of the fish to avoid obstacles while swimming backwards. The hind end and particularly the finger-like tail are known to contain tissues corresponding to an electric organ; it seemed of interest to consider whether this organ may enable the animal to detect objects in the vicinity of its body.