A COMPARISON OF GILL AND HEMOLYMPH ASSAYS FOR THE THIOGLYCOLATE DIAGNOSIS OF PERKINSUS-ATLANTICUS (APICOMPLEXA, PERKINSEA) IN CLAMS, RUDITAPES-DECUSSATUS (L) AND RUDITAPES-PHILIPPINARUM (ADAMS-ET-REEVE)

Gill and hemolymph assays for the thioglycollate diagnosis of Perkinsu s atlanticus in clams (Ruditapes decussatus and Ruditapes philippinaru m) were compared. Gills, hemolymph and the body remains from clams wer e separately incubated in fluid thioglycollate medium and stained with iodine solution. The intensity of infection was evaluated using the t raditional semi-quantitative scale and a recent quantitative technique based on sodium hydroxide digestion of incubated tissues. The semi-qu antitative scale was also compared with paraffin histological analysis . No one method detected all of the infections which were found by one or more of the techniques used. The hemolymph assay detected 69%, the gill analysis 90% and the body remains analysis 95% of all infected c lams. Of all negative diagnoses from hemolymph, gills and body remains , 46%, 22% and 13%, respectively, were false. Diagnoses by histologica l sections only detected 61% of positive gill tests. The semi-quantita tive Mackin's scale from gill assay exhibited exponential relationship s with total body burden. The quantitative gill, hemolymph and body re mains analysis showed linear correlations with total clam body burden after a logX-logY transformation of the data. Results suggest that the gill tissue is better than hemolymph to diagnose P. atlanticus in cla ms. The semi-quantitative method from gills is easy and shows a high e fficacy, but to evaluate infection intensity and avoid false negative diagnoses it is necessary to calculate the total body burden.