Agonistic sounds and swim bladder morphology in a malapterurid electric catfish

摘要: Several catfish families possess an elastic spring apparatus (ESA) morphology that is assumed to function as a swim bladder drumming sound production mechanism. Although they have ESA, sounds in the electric (Malapteruridae) not been described. We recorded several different types Malapterurus beninensis and we examined of bladder, ESA ultrastructure protractor muscle. The muscle contains small rounded fibers with abundant mitochondria, narrow myofibrils, elaborated sarcoplasmic reticula sometimes cores. Contractions should pull Mullerian ramus (MR) attached anteriorly. Further, MR possesses anterior fulcrum abuts upon vertebral complex. were elicited during agonistic interactions laboratory. observed ratchet, click train mouth sounds. Mouth are single event, low-frequency (mean dominant frequency 176 Hz) coincide bite-like motion. Ratchet high-frequency 1568 3739 Hz, respectively) occur trains. characteristics indicative muscle-driven predicted by morphology. propose hypotheses for these mechanisms. Click sounds, particular, could result from gas movement through neck between posterior chambers.