Cellular and subcellular localization of chromium in the crab Liocarcinus puber (Brachyrhyncha) by transmission electron microscopy, secondary ion mass spectrometry and electron microprobe analysis

Abstract

The swimming crab Liocarcinus puber (Crustacea Brachyrhyncha) was exposed for 2 weeks to CrCl3 (chromium occurs principally in the trivalent state in the natural environment). The gills, digestive gland and muscle were examined by several analytical techniques for cellular and subcellular localization of chromium. The techniques applied were secondary ion mass spectrometry (ion microscopy and ion microprobe analysis) associated with photon microscopy and X-ray spectrometry (electron microprobe analysis) together with transmission electron microscopy. The digestive gland was found to be free of chromium, whereas chromium was adsorbed onto the gill exoskeleton. The muscle was the only tissue with intracellular electron-dense precipitates with no surrounding membrane. The metal was detected in the heterophagic vacuoles of amoebocytes where it was associated with phosphorus and trapped in an unsoluble form. Mechanisms of chromium cellular and subcellular metabolism were compared between crabs and other aquatic organisms. L. puber does not appear to be a suitable bioindicator of chromium pollution because of molting and its low chromium bioaccumulation capability.