Cuticular ultrastructure of Paragonimus from Costa Rica

The surface ultrastructure of eggs, metacercariae, and adults of Paragonimus endemic to Costa Rica were examined under the scanning electron microscope. Two different morphological types of parasites were found. The most commonly found form was the "first type" (86%) corresponding to the previous descriptions of P. mexicanus. The metacercariae of this type showed an oral sucker surrounded by papillae clustered on the dorsal lip, the ventral sucker showed six internal and from 30 to 35 external papillae. The most evident difference in the "second type" was observed on the ventral sucker, because it showed an intermediate row of five to six papillae located between the internal and external papillae. In conclusion, the Paragonimus species of Costa Rica is P. mexicanus. The morphological differences seen could be a variation of the same species or another species.