New species of macrocercous and megalurus cercariae infecting the freshwater snail, Paludomus (Paludomus) tanschauricus (Gmelin, 1771) in Malabar, Kerala

The present paper describes two new species of cercariae infecting the freshwater snail, Paludomus (Paludomus) tanschauricus from Malabar, Kerala. Paludomus tanschauricus collected from the hill streams at Vattakkundu in the Wayanad district of Kerala harboured a macrocercous cercaria, Cercaria sp. XX Malabar n. sp. characterized by a disproportionately large tail. Developmental stages were recovered from the hepatopancreatic tissues of the snail host. Cercariae encysted on the gills of the fish, Haludaria melanampyx. Snails collected from Papanashini rivulet at Thirunelli, also from Waynad district were infected with a megalurous cercaria, Cercaria sp. XXI Malabar n. sp. possessing an elongated tail with an adhesive cup-like sucker at its tip. Redial stages developed in the hepatopancreas while the cercariae were found to encyst on any available substrate. The morphology and morphometry of these two cercariae along with their developmental stages are studied in detail and compared with related species to establish their systematic positions.