Histopathological alterations in gills of juvenile Florida pompano Trachinotus carolinus (Perciformes, Carangidae) following sublethal acute and chronic exposure to naphthalene

Abstract

Juvenile Florida pompanos (Trachinotus carolinus) were exposed to sublethal concentrations of naphthalene (0.15 ppm and 0.30 ppm) for 24 hours (acute) and 12 days (chronic). Control fish were maintained for the same periods in clean seawater and seawater with ethanol, which is a carrier to dissolve naphthalene. Gill samples from 56 fish were prepared for histological analysis and examined under optical and scanning electron microscopy. Alterations in the gills of fish exposed to naphthalene were semi-quantitatively ranked based on the severity of tissue lesions and comparisons were made with fish kept in clean water and water with ethanol. Fish of the control groups exhibited functionally normal gills, apart from sparse, slight alterations, such as the lifting of epithelial cells. Acute exposure to naphthalene caused slight to moderate alterations in the gills, whereas chronic exposure led to significant, progressively irreparable damage, especially at the greatest concentration. Chronic exposure resulted in a greater number and diversity of alterations. Hypertrophied epithelial cells, epithelial lifting, telangiectasia, fusion of secondary lamellae or their tips, rupture of lamellar epithelium, stasis and necrosis were the most common lesions. Naphthalene caused severe damage to the gills of the Florida pompano which was related to concentration and exposure time.