Digestive plasticity of the marine benthic omnivore Nereis virens

Abstract

We investigated plasticity in the digestive chemistry of the omnivorous marine benthic polychaete Nereis virens. We sought to compare the previously observed variability among species (genotypic plasticity) versus the variability within a species (phenotypic plasticity) in response to changes in diet. We found statistically significant changes in enzyme activities between worms given carnivorous versus detritivorous diets. These changes were smaller in magnitude than the among-species range, but consistent in direction. The surface tension of the gut fluid was largely unaffected by diet. However, the presence of surfactant micelles was closely linked to the presence of sediment in the diet. These results suggest that sediment ingestion induced the introduction of high concentrations of surfactants into the gut lumen, perhaps related to the adsorption of digestive agents and products onto the mineral matrix. In the context of the among-species trends found by Mayer et al. (Digestive environments of benthic macroinvertebrate guts: enzymes, surfactants and dissolved organic matter. J. Mar. Res. 1997;55(4):785–812.), Nereis virens shows greater phenotypic plasticity in its surfactant secretion than in its enzymatic response to varying food types.