Sound production and localization in loricariid catfishes.

Abstract

Catfishes of the family Loricariidae have bilobed swim bladders that are adjacent to their ears. We hypothesize that this anatomical design assists these fishes in sound localization and/or sound production. Loricariid catfishes produce short, broadband clicks via pectoral spine stridulation. To test whether these clicks can be localized, we used classical conditioning to train groups of 50 Otocinclus affinis to come to a conspecific sound on one side of a 200‐L aquarium. Four types of experiments were performed—naive, trained, test‐1, and test‐2. During trained trials, food and a conspecific sound stimulus were presented simultaneously, while only the sound stimulus was presented during naïve (untrained) trials. During the test‐1 and test‐2 trials, only the conspecific sound stimulus or a 500‐Hz sound stimulus, respectively, was presented. O. affinis were attracted to the conspecific sound post‐training, with 60–80% of the fish remaining on the speaker side of the tank during the stimulus. In summary, O. affinis are able to localize a conspecific sound source. Future experiments have been designed to examine the acuity of this sound localization using four speakers in a circular tank, and the effects of swim bladder deflation on the sound localization ability of O. affinis.