Low pH alters response to food in the crayfish Cambarus bartoni

Abstract

In a relatively acid-tolerant crayfish, Cambarus bartoni, locomotory response to food, and associated antennular flicking, were tested at both a circumneutral and a sublethal acid pH. Crayfish were run through a Y maze at pH 7.5, 4.5, and again at 7.5. One arm of the Y maze contained food; the other did not. The time to complete the maze at pH 4.5 increased significantly compared with the time taken at pH 7.5 (P < 0.001). Once pH was restored to 7.5, the time to complete the maze was greater than the initial control at pH 7.5 (P < 0.001) but less than pH 4.5 (P < 0.05). At pH 7.5, 73% of the crayfish chose the food arm; at pH 4.5, 33% chose the food arm; and when pH was returned to 7.5, 46% chose the food arm. Antennular flicking frequency was greatest at pH 7.5 and significantly less at 4.0 (P < 0.0001). Once pH was restored to 7.5, flicking rates were significantly lower than those in the first trial at pH 7.5 (P < 0.01), but significantly greater than those at pH 4.0. Decreased antennular flicking and possible avoidance of food at a sublethal pH (4.0) imply that either chemoreception of food cues or normal central processing of chemical input is seriously impaired.