Brainstem acoustic areas in the marine catfish, Arius felis

The marine catfish Arius felis produces low frequency sounds for communicat ion and obstacle detection. It was hypothesized that the utriculus of the i nner ear might play an important role in these behaviors. In the current st udy, brainstem acoustic areas were studied to reveal possible neuroanatomic al specializations in utricular processing areas. The first-order octaval n uclei in Arius were identical in number, anatomical characteristics, and or ganization of saccular, lagenar, and utricular inputs to previous reports o f these features in Ictalurus, a closely related species of catfish that do es not exhibit the specialized acoustic behaviors present in Arius. Similar ly, injections of neural tracer in the acoustic midbrain (nucleus centralis ) of Arius revealed afferent and retrograde pathways almost identical to th ose previously reported in Ictalurus. It is suggested that areas within the primary and higher-order octaval nuclei that utilize utricular input in ac oustic processing are likely identical in Arius and Ictalurus. Two sets of higher-order connections in Arius differ from those in Ictalurus. First, Ar ius apparently lacks the direct input from the anterior octaval nucleus to nucleus centralis reported in Ictalurus. Second, in Arius nucleus centralis projects bilaterally to a strip of neurons positioned ventral to the ventr al boundary of the torus sernicircularis. This projection is apparently abs ent in Ictalurus and in the related species Carassius (goldfish), but has b een previously reported in Porichthyes, a sound-producing species belonging to a different teleost taxon. Copyright (C) 2001 S. Karger AG, Basel.