Variations in biochemical composition of juvenile Ruditapes philippinarum infected by a Vibrio sp.

Abstract

The biochemical composition of young Ruditapes philippinarum was examined in 2 groups of clams, healthy clams and those experimentally infected with the pathogenic Vibrio Pl bacterium, to document utilization of biochemical reserves in individuals affected by 'brown ring disease'. After 1 mo of starvation, refeeding half of the experimental clams induced recovery as determined by the absence of visual signs of disease. Disease was associated with decreased dry weights in both fed and starved individuals (from 41 down to 30-35 mg clam-1) Glycogen was found to be the main biochemical reserve used by diseased individuals. A significant decrease in glycogen (from 45 down to 20-25 mg g-1 dry wt) was observed in infected clams. Lipid and protein amounts were related to nutritional conditions In refed individuals, carbohydrate reserves were low in spite of some recovery. These results could indicate an irreversible change of the digestive gland manifested by the inability to store reserves and distribute them to other tissues. In the field, mass mortalities observed in infected populations could result from the degeneration of metabolic activity.