An Electrical Receptor in Fishes

Abstract

CERTAIN families of fishes, namely the Mormyridæ of tropical Africa and the Gymnotidæ of Central and South America, possess a small electric organ which exhibits intermittent activity. Lissmann¹ found that Gymnarchus niloticus Cuv., swimming freely, emitted pulses at an even rhythm of about 300 per sec.; the frequency was unaffected by the activity of the fish. Similar observations have been made on six species of the Gymnotidæ by Coates et al.² and Coates³, who found regular rhythmic discharges the frequency of which varied with the species and ranged between 65 and 1,000 per sec. Again, the rhythm was unaffected by the activity of the fish. Coates⁴ also reported a low-voltage discharge at about 50 per sec. from Electrophorus electricus. Mormyrus kannume has been reported to discharge pulses at a low rate when resting and at 80–100 pulses per min. when disturbed^5,6.