Hypoxia has lasting effects on fast startle behavior of a tropical fish, (Haemulon plumieri)

Abstract

Summary statementThis study describes for the first time long-lasting behavioral effects of hypoxia on a tropical fish, the white grunt (Haemulon plumieri) from Puerto Rico.\n\nAnthropogenic activities and climate change have resulted in an increase in hypoxia in nearshore ecosystems worldwide. The San Juan Bay Estuary System in Puerto Rico is one such ecosystem that has undergone an increase in hypoxic events over the past few years. We collected white grunts (Haemulon plumieri) from one of the estuary lagoons to study the effects of hypoxia on fast startle responses (fast-starts). We hypothesized that exposure to hypoxia would significantly decrease the frequency of fast-starts evoked by an abrupt sound stimulus. After an exposure to an oxygen concentration of 2.5 mg L-1 (40% of air saturation), there is a significant reduction in the frequency of fast-starts that is maintained for at least 24 h after the exposure. Exposure to a random sequence of oxygen levels of 5.0, 4.3 and 3.7 mg L-1 (80, 70, and 60% of air saturation) did not show a significant effect until one hour after exposure. We speculate that the lasting effect of hypoxia on fast-starts, thought to be involved in escape, will result in a greater susceptibility of the white grunt to predation. We have identified the Mauthner cell, known to initiate fast-starts, to allow future studies on how low oxygen levels impact a single cell and its circuit, the behavior it initiates and ultimately how changes in the behavior affect population and ecosystem levels.