RECOVERY OF THIRD-STAGE LARVAE OF ANGUILLICOLA CRASSUS (NEMATODA : DRACUNCULOIDEA) FROM THE FLESH OF FISHES : ASSESSMENT OF A DIGESTIVE MEDIUM AS A TOOL FOR THE STUDY OF FISH PARATENIC HOSTS.

The purpose of this study was to recover third-stage larvae (L3) of Anguillicola crassus alive from the flesh of fishes. Different digestive media have been tested on eel flesh for their efficiency and on living infective third-stage larvae for their harmlessness. The results were : (1) Long-term survival of the L3 larvae was low, but their morphological features were recognizable in each digestion runs. (2) Pepsin concentrations between 2.5 and 40 g/l proved to be without influence on the short-term (2-4 hours) survival of the L3 larvae of A. crassus. The digestion of the eel flesh was more advanced with the most concentrated media, when applied for 12 hours. (3) L3 larvae survived longer at pH 1.8 than 1.5, and digestion appeared to be faster at the upper pH level. (4) L3 larvae survival was much longer at 20°C than at 30°C, but efficiency of the digestion process was poor at the lower temperature. For epidemiological studies, the optimal factors combination has been established at pepsin concentration : 10 g/l, pH : 1.8 and temperature : 20-22°C, particularly when quantitative recovery of L3 larvae and work efficiency were taken into account.