Cadmium toxicity assessment based on a climbing behaviour test with intertidal periwinkles, Littorina littorea (L.).

The present investigation was carried out to develop a climbing behaviour test with periwinkles, Littorina littorea. Sublethal exposure to pollutants may jeopardize the ability of this intertidal mollusc to climb up to below the water surface and remain attached to the substrate to defend against waves and predators, which is an ecologically relevant effect. The total climbing distance covered for 8 hr (TCD-8), the cumulative climbing activity (CCA) and the tenacity of attachment (ToA) index were shown to exhibit dose-dependent changes on exposure to sublethal concentrations of Cd. Periwinkles in control groups showed a tendency to climb and locate at the air-water interface, but they tended to sink and to reduce their climbing activity at increasing Cd concentrations. Cadmium was accumulated in digestive gland-gonad complex and foot in a dose-dependent manner. Histological examination of Cd-exposed periwinkles revealed that mucous glands were exhausted, and muscle tissue disorganized in the foot, with signs of a general stress response in the digestive gland (epithelial thinning, digestive cell vacuolisation, basophilic cell hyperplasia and inflammatory nodes). Thus, locomotion impairment (altered foot tissue integrity), general weakening (sublethal toxicity), or a combination of both could be the cause of the observed effects of Cd on the climbing behaviour.