Meeting Abstract

103.3  Saturday, Jan. 7  Navigation through obstacles by bluegill sunfish under different sensory conditions FLAMMANG, B.E.*; LAUDER, G.V.; Harvard University; Harvard University

Numerous studies have shown that the pectoral fins of bluegill sunfish act in a propulsive role, especially during swimming at slow speeds. In order to assess if sunfish are also capable of using their pectoral fins for tactile sensory input and to navigate through obstacles, we created two obstacle courses through which they swam under different water speed and sensory input conditions. The first obstacle course was a maze of alternating 2 cm diameter posts, 4 cm apart on center, through which the fish swam through at flow speeds of 0.0, 0.5 and 1.0 Ls-1. Four fish each swam through the first obstacle under four treatment conditions: 1) with no modifications, 2) in complete darkness (filmed in infra-red) with lateral line intact, 3) lights on and lateral line knocked out with cobalt chloride, and 4) in complete darkness with the lateral line knocked out. A second set of experiments using an obstacle course with a narrowing angled entrance and long corridor was used to test the limit to the narrowness of a passageway through which a fish would swim forward and backward. Under normal conditions (in the light with lateral line intact), fish tapped obstacle posts as they passed them, reaching out with their fins to make contact with the obstacles. With reduced visual and lateral line input, fish tapped posts more frequently, for shorter periods of time, and swam through the obstacle at slower speeds. The limit to the narrowness of a passage through which a fish would swim was the width of its body. Flexibility of pectoral fins was important to permit fish to hover in confined spaces. These data provide behavioral evidence that fish actively use input from pectoral fin bending to assist in navigating through complex cluttered environments.