Red Childress
03-16-2009, 02:19 PM
The muskellunge, Esox masquinongy, is a predatory esocid fish with well-developed visual and lateral line systems. The purpose of this study was to determine the relative roles of these two sensory modalities in organizing the strike behavior of the animal. Subadult muskellunge were videotaped in a test arena while feeding on fathead minnows (Pimephales promelas). Animals were tested under five conditions: 1) control animals in which the visual and lateral line systems were intact; 2) animals with lateral line afference suppressed by immersion for 12-24 h in 0.1 mmol l(-1) CoCl2; 3) animals blinded by bilateral optic nerve transection; 4) animals that had been unilaterally blinded; and 5) animals in which the lateral line system had been unilaterally denervated. The feeding behavior of the muskellunge consists of two phases: a slow stalk of the prey with minimal body movement followed by an explosive C- or S-start lunge at the prey. Quantitative comparisons of animals in the five test groups indicate that, although vision is used in the initial acquisition of the prey, both vision and the lateral line system play important roles in determining the initiation of the rapid strike. The lateral line system may play a critical role in the final capture of the prey at the end of the strike. In addition, lateral-line-suppressed muskellunge strongly alter their approaches to more distant prey. Bilaterally blinded muskellunge do not stalk their prey, but will lunge only at prey that are at close range. Unilaterally blinded or denervated muskellunge also alter their detection of and approach to prey, attending to a wider region of the intact sensory hemisphere. Our data suggest not only that the visual and lateral line systems play complementary roles in the feeding behavior sequence but also that each system plays a more or less dominant role during consecutive phases of the behavior.