Body Condition in MaleBetta splendensDoes Not Predict Their Ability to Perform Opercular Displays Under Hypoxic Conditions

Abstract

Many fish, including the fighting fish Betta splendens, perform a display in which the opercula are extended away from the head and gills. Previous work has shown that opercular display rates by male B. splendens decrease under conditions of reduced dissolved oxygen (hypoxia). We tested the hypothesis that the ability to maintain opercular display rates under hypoxic conditions is related to body condition in male B. splendens. We also tested the hypothesis that females would show a greater preference for males performing this display under hypoxic conditions, when the display should be a more reliable indicator of male phenotypic quality. We found no evidence to support either hypothesis. Male opercular display rate in hypoxic conditions was unrelated to natural or experimentally induced variation in body condition. Female B. splendens showed no differential preference for the opercular display, assessed through the use of computer animated male stimuli, in either acute or chronic hypoxia. We conclude that the presence of an air-breathing organ in this species makes the opercular display an unreliable signal of male quality as measured by body condition.