FURTHER STUDIES OF THE AGGREGATING BEHAVIOR OF AMEIURUS MELAS

Abstract

Catfishes showed no discrimination by contact between a scoured stone and an inactive catfish, nor between a paraffined and non-paraffined stone, but gave a negative reaction to models of paraffin mixed with India ink. There is no evidence for a gustatory element in the stimulus which one catfish receives from another. A gustatory stiinulus acts only to produce a negative reaction when some unfavorable chemical is present. The positive responses which blinded catfishes give to one another in passing are eliminated by isolation for 20 days, but reëstablished in a few minutes when the fishes are placed together. Touch responses by blinded catfishes are positive immediately after isolation when contact is gentle enough to prevent shock. The reactions of blinded fishes to one another due to a response to water vibrations, may be a conditioned response developed after the loss of eyesight, and is probably not effective among normal fishes. The sight response of normal fishes to one another was not completely eliminated in all individuals by 161 days of isolation, although it was much less marked. It was reëstablished in the course of a few minutes, usually soon after contact occurred. This sight response may be instinctive but is probably subject to modification by conditioning to some extent at least. A satisfaction evidently accrues to the catfishes from the mutual contact and pressure of the aggregations, and the importance of the thigmotactic response in these reactions is emphasized by these observations. A comparison of the respiratory rate of catfishes, both normal and blinded, for a period of one hour gave no significant difference between the grouped and isolated individuals.