Petroleum hydrocarbons are toxic to marine invertebrates when present above a threshold level in the marine ecosystem. The major detoxification organ in shrimps is the hepatopancreas, which has been used as an indicator organ for toxicity assessment. The effects of Bombay High Crude on the morphology of hepatopancreatic tubules of Metapenaeus dobsoni when examined under the light and electron microscopes reveal a series of changes indicating that the cellular compensatory mechanism is activated by low or sub lethal doses of hydrocarbons. At the high sub lethal dose of 8 ppm the cellular detoxification mechanisms fail resulting in severe structural damage. The changes indicate that they are dose and time related histopathological responses. Changes such as an increased presence of B - cells towards the distal end of the tubule, substantial increase in the number of F/B cells, extensive cytrorrhexis, reduction in the number of E- cells. vacuolation of E-, R- and F- cells are changes which can be detected under light microscope along with the presence of pyknotic nuclei, storage of large lipid droplet in combination with cells voided of other subcellular components, proliferation and distortion of Golgi apparatus and mitochondria which were detected in the ultrastructure study can be used as biomarkers of stress caused by petroleum hydrocarbon pollution.

Metapenaeus dobsoni, hepatopancreas, histopathology, petroleum hydrocarbons.