Short-term effects of food availability on air-breathing frequency in the fish Corydoras aeneus (Callichthyidae)

Abstract

To examine the hypothesis that breathing patterns in fish capable of bimodal respiration can be modified by ecological factors that alter the relative costs of air and water breathing, we determined the air-breathing frequency and activity of a group of Corydoras aeneus before and after presentation of small amounts of food. In nature a reduction in air breathing while feeding on small, patchy resources should reduce loss of food to competitors and lower the risk of failing to relocalize the food source. Activity always increased after food presentation, but the change in air breathing depended on dissolved oxygen tension. Air breathing decreased after food presentation at 116 and 72 torr (1 torr = 133.322 Pa), stayed the same at 44 torr, and increased at 24 torr. This suggests that although oxygen demand increases during feeding, air breathing is decreased when the ambient conditions permit a compensatory increase in the uptake of dissolved oxygen.