PAPYRUS SWAMPS AND VARIATION IN THE RESPIRATORY BEHAVIOR OF THE AFRICAN FISH BARBUS-NEUMAYERI

Wetlands, dominated by papyrus (Cyperus papyrus), are extensively dist ributed in east and central Africa. However, the use of papyrus swamps by fishes is limited to species that can tolerate the low oxygen cond itions that can prevail in the dense swamp interior. In this study, we ask whether the patchy distribution of papyrus swamps may contribute to variation among fish populations in traits related to oxygen uptake . A series of paired experiments was used to compare the respiratory b ehaviour of a small water breathing cyprinid Barbus neumayeri from the dense interior of a papyrus swamp in Western Uganda, to populations f rom nearby well-oxygenated rivers and streams. The respiratory behavio ur of the swamp population differed from the other populations. Severa l lines of evidence suggest that B. neumayeri from papyrus swamps are more tolerant of low oxygen conditions than populations from nearby ri ver and stream sites, including lower thresholds for aquatic surface r espiration in the swamp population, lower gill ventilation rates in th e swamp population and higher loss of equilibrium in fish from the riv er/stream sites. This small scale geographical variation in behaviour among B. neumayeri populations supports an earlier study that document ed variation in gill morphology among sites that differed in oxygen av ailability, and supports the significance of papyrus swamps in promoti ng diversification among populations.