Influence of oxygen levels on the predatory behaviour of the isopod saduria entomon

Abstract

The effect of low oxygen levels on predatory behaviour of the isopod Saduria entomon on its natural prey, the amphipods Monoporeia affinis and Pontoporeiafemorata, was studied in laboratory experiments. The isopod S. entomon consumed the amphipods M. affinis and P. femorata in normoxic experimental conditions. A significantly decreased predation rate was found at 33% oxygen saturation and below. No preference by S. entomon for either amphipod species was detected, and both amphipod species appeared to use a similar behavioural strategy for avoiding predators at low oxygen concentrations. At a low oxygen concentration (8%) S. entomon was mostly immobile on the sediment surface, and its predation rate was low. There was no indication that low oxygen levels increases the vulnerability of M. a ffinis or P. femorata to predation by S. entomon. Instead, the findings suggest decreasing rates of predation as the oxygen concentration declines.