Ethoxyresorufin-O-deethylase enzyme activities and accumulation of secondary/tertiary lysosomes in rabbitfish Siganus oramin as biomarkers for xenobiotic exposures

Abstract The sensitivities of using hepatic and intestinal ethoxyresorufin- O -deethylase (EROD) activities and hepatic accumulation of secondary/tertiary (2°/3°) lysosomes to detect xenobiotic exposures were assessed in the rabbitfish Siganus oramin in a metropolitan harbour, subtropical Hong Kong, over a complete seasonal cycle of one year. Additional information on the body-burden pollutants and physiological indices in S. oramin , and seasonal variables in seawater quality, were extracted from published data and re-analyzed. Under the influences of pollutant cocktail and seasonal factors, neither the hepatic nor intestinal EROD activity was indicative of total polycyclic aromatic hydrocarbons (∑ PAH), total polychlorinated biphenyls, condition factor and hepatosomatic index (HSI) in S. oramin . However, the relative ratio of hepatic to intestinal EROD activities provided an indication to differentiate the xenobiotic intake route in the fish through diffusion via gills/skin or consumption of contaminated food. In addition, the elevated hepatic accumulation of 2°/3° lysosomes was closely associated with the dominant temporal trends of zinc and ∑ PAH, as well as reduced HSI, in S. oramin . Being minimally influenced by any investigated seasonal factors, the hepatic 2°/3° lysosomes in S. oramin was recommended as an effective biomarker of xenobiotic exposures and toxic effects for use in coastal pollution monitoring programmes.