The effects of mercury exposure on the surface morphology of gill filaments in Perna perna (Mollusca : Bivalvia)

This study investigated the possibility that changes in the surface morphol ogy of mussel (Perna perna) gill filaments may be used to indicate the rela tive toxicity of pollutants in the marine environment. Healthy, adult P. pe rna were collected and immersed in 2 free-flow tanks. Mercury was added to seawater as it entered tank 1 to achieve a constant level of 50 mu g/1(-1) over 24 days. Uncontaminated sea,vater was circulated over the mussels in t ank 2 (control) for the same period. A 25 mm(2) area of gill filament was r emoved from each of the 5 specimens before and after 24 days immersion in t ank 2, and after immersion for 1, 2, 4, 8, 16 and 24 days in tank I. These mere examined using a scanning electron microscope. The remaining soft tiss ues from each animal were analysed for mercury using an atomic absorption s pectrometer. Mercury concentration increased from 0.13 (pre-immersion) to 8 7 mu g/g after day 24. Surface morphology remained normal for all animals i n tank 2 and for those exposed to Hg for up to 8 days, However, from 16 to 24 days exposure there was a gradual increase in the diameters of microvill i, a depletion of abfrontal cilia, an increase in abnormal, perhaps necroti c cells and an unusual increase in the number of cilia on the lateral surfa ces. These results confirm that P. perna is an efficient bio-accumulator an d suggest that their gill pathomorphology mag be a useful indicator of toxi city (C) 1999 Elsevier Science Ltd. All rights reserved.