Morphometrics and gill function in Gammarus duebeni (Peracarida: Amphipoda) inhabiting a sewage treatment works

Abstract

Gills from a population of Gammarus duebeni (Liljeborg), isolated after colonising the humus tanks of a sewage treatment works, were measured by image analysis and compared with those from a population in an adjacent estuary. Gill length, width, perimeter, area and lamellar area were all significantly larger for amphipods inhabiting the sewage treatment works compared with their estuarine counterparts (believed to be the parent population). However, the relative contribu- tion of lamellae to overall gill area was smaller in individuals from the sewage works, indicating that the peripheral sinus that surrounds the gill is wider in this population. Humus tanks constitute an extreme environment compared with the adjacent estuary, having constant hypoxia and elevated concentrations of dissolved trace metals, particularly zinc. Accumulation of zinc was examined in sewage works G. duebeni following different periods of acclimation to 'clean' water, to test whether differences in gill morphometrics were accompanied by differences in gill physiology/function. Amphipods acclimated to 'clean' water for 6 and 10 wk accumulated less zinc than those without acclimation. Exposure salinity also affected zinc accumulation, but no clear trends were discernible. Increased gill size in sewage works amphipods indicates that oxygen uptake is more critical than minimising metal uptake for G. duebeni inhabiting the humus tanks. However, there are no obvious explanations for the effects of acclimation or salinity on metal uptake.