Behaviour of some intertidal molluscs exposed to water soluble fractions of diesel

The behaviour of three intertidal molluscs exposed to water soluble fractions of diesel were studied. The rate of crawling of Cerethidea fluviatilis decreased with an increase in concentration and the animals were completely immobilized at the highest dosage (50%). The burrowing ability of Katelysia opima was found to be suppressed in three different concentrations (25,50 and 75%). Smaller individuals (15–20 mm) appearing to be less sensitive than larger forms (20–25 mm). Byssal thread production in Perna viridis was significantly depressed in all concentrations, except the lowest doses of toxicant (5%), where slight stimulation was observed only with smaller sized individuals (20–30 mm).