Differing sensitivities of respiratory and osmoregulatory gill tissue of Carcinus maenas (Crustacea: Decapoda) to water-borne copper

Abstract

Following a 14 d exposure to sublethal concentrations of copper [0 (= control), 50, 100, 200, 300, 500 μg l−1] in a static laboratory system, Gills 5 and 8 of the common shore crab Carcinus maenas (L.) were removed and examined for damage by transmission electron microscopy. In this species, the anterior gills (1 to 6) are primarily respiratory in function, while the posterior gills (7 to 9) have an additional osmoregulatory role, with the respiratory epithelia being restricted to areas proximal to the marginal canal. The first signs of damage (epithelial hyperplasia, necrosis, vacuolation, haemocyte infiltration) occurred at 100 μg Cu l−1, but only in the respiratory gill (5) and only in areas close to the marginal canal. At 200 to 500 μg Cu l−1, these ultrastructural changes spread progressively throughout the lamellae of the respiratory gill. No damage was observed in the osmoregulatory gill (8) until 300 μg Cu l−1, and structural disruption, similar to that seen in the respiratory gill at 100 μg Cu l−1, was not observed until exposure to 500 μg Cu l−1; lipofuscin granule formation was seen in the osmoregulatory gill following exposure to 300 and 500 μg Cu l−1. The physiological implications of the differing sensitivities of the two gill types to water-borne copper are discussed.