Limpet mucus as a depuration route and potential biomonitor

Metal granules have previously been found in the mucus trails of gastropods . We hypothesised that such metals could be a marker of environmental pollu tion and that mucus may constitute a depuration route. We investigated this using limpets from sites in north-east England. Mucus production generally showed a significant logarithmic correlation with flesh dry weight of limp et but there was an up to 4-fold inter-site variation. Mucus production did not vary in any systematic way with metal content of either mucus or flesh . X-ray microanalysis revealed that Ca, Cl, S, K, P, Si, Mg and Fe were wid ely distributed in mucus across sites. Aluminium, Cr, Cu, Mo and Ni were al so detected, but at lower frequencies. Ion chromatography analysis of metal s in mucus (Cd, Co, Cu, Ni, Pb, Zn) indicated that Pb was dominant. In gene ral, metals with levels > 10 mu g g(-1) were found at sites close to the po lluted Tees estuary. In limpet flesh, the dominant metal was Fe and again m etal levels were generally highest close to the Tees. Where comparisons can be made, metal levels in mucus were typically higher (by up to 2000x) than those in the flesh. Metal levels in mucus showed little correlation with f lesh dry weight or with metal levels in limpet flesh. The high levels of Pb and other metals in mucus, relative to the flesh, may suggest that mucus f unctions as a depurator, animals releasing as much Pb per day in mucus as i s stored within the flesh. Mucus has the potential for use as a non-destruc tive biomonitor that allows for repeat and instantaneous measurements.