Many studies have been made on the metabolism of polycyclic aromatic hydrocarbons in mammals and it has been shown that these animals can convert compounds such as naphthalene into several metabolites (see, for example, Corner & Young, 1955). Baldwin (1957) has remarked on the ability of mammals to metabolize substances that they are unlikely to meet ‘except through the medium of the laboratory’. Marine animals, how-ever, can encounter these compounds in their normal environment, considerable quantities of polycyclic aromatic hydrocarbons being present in crude oil (Boylan & Tripp, 1971), in which form substantial amounts must be released into the sea annually.

Little work has been done on the metabolism of naphthalene in marine animals, apart from studies confined – as far as we are aware – to experiments with three species of fish (Lee, Sauerheber & Dobbs, 1972) and the mussel Mytilus edulis L. (Lee, Sauerheber & Benson, 1972). Data obtained using fish were consistent with those of earlier studies with mammals in showing that the hydrocarbon is converted into hydroxylated derivatives: but no evidence of naphthalene metabolism was found in the experiments with Mytilus. Indeed, until the present work, the only species of invertebrate that has been found to metabolize the compound is the housefly Musca domestica L. (Terriere, Boose & Roubal, 1961).

The present study, using Maia squinado (Herbst), has been carried out as part of a general investigation of the accumulation of polycyclic aromatic hydrocarbons in marine food chains and was designed to establish whether a marine crustacean possesses a means of metabolizing naphthalene by converting it into soluble excretion products.