Laterophysic Connection: A Unique Link between the Swimbladder and the Lateral Line System in Chaetodon (Perciformes: Chaetodontidae)

Abstract

The auditory and lateral line systems of teleost fishes are complementary in their ability to detect mechanical stimuli in water (Kalmijn, 1988, 1989; Coombs, 1994). The lateral line system is normally sensitive only to local incompressible flow fields arising from predators, prey, neighbors in a school, and environmental obstacles (reviewed by Montgomery et al., 1995). In contrast, the otolithic organs of the inner ear respond to whole-body accelerations generated by the same local flow fields to which the lateral line system responds. Enhanced sensitivity of the inner ear to propagated pressure waves (sound) is a specialized function of the inner ear of teleost fishes (Kalmijn, 1989), which is the result of the presence of a volume of compressible fluid (i.e., the swimbladder) in the vicinity of the inner ear. Morphological specializations in which the swimbladder is brought into close or direct contact with the inner ear are generally known as otophysic connections and occur in some or all species in all four lineages of teleost fishes (Osteoglossomorpha, Elopomorpha, Clupeomorpha, Euteleostei, reviewed by Schellart and Popper, 1992). It seems reasonable that the lateral line system could also be made pressure sensitive by placing an air cavity in the vicinity of, or in direct contact with, a lateral line canal. There are only two known examples of this type of sensory specialization: the recessus lateralis of clupeomorph fishes; and the unique connection between the inner ear and the lateral line