Ultrastructural and phylogenetic characterization of some trematode cercariae emerging from the freshwater ampullariid snail, Lanistes carinatus (Olivier, 1804).

Ampullariid snails act as the first intermediate host for many intestinal parasites, such as Stomylotrmatidae, Phaneropsolidae, and Echinochasmidae. Both the Stomylotrmatidae and Phaneropsolidae families had the xiphidiocercariae type in their life cycle, while the Echinochasmidae had gymnocephalus cercaria type. Freshwater snails (Lanistes carinatus) were collected from Al-Inaniyyah, a village in the Damietta Governorate. The cercaria types were harvested by exposing the naturally infected snails to a strong artificial illumination for 2 h. This study added ultrastructure description and molecular structure of the 28S rRNA gene for the emerging cercariae types. This study included two types of cercariae that emerged from the freshwater snail Lanistes carinatus (xiphidiocercariae and gymnocephalus cercaria types). The oral sucker of the first type is armed with xiphoid-spine. While the oral sucker of the second type of cercariae was decorated with non-ciliated sensory papillae and is armed with spiny collar. The phylogenetic positions were inferred by the sequencing the 28S rRNA gene. The sequences of the xiphidiocercariae were linked to Stomylotrema pictum (family Stomylotrmatidae) and Phaneropsolus praomidis (family Phaneropsolidae), while, the sequence of the gymnocephalus cercariae was related to the family Echinochasmidae.