Metacercaria of Tylodelphys sp. a member of the Diplostomidae, was 
isolated naturally from the gas bladder of Lates niloticus (Nile Perch),
found in Lake Nasser (southern Egypt). The morphology, ultrastructure, 
and genomic characterization were investigated and described. The main 
characteristics were shown by the light microscope and these were 
confirmed by the electron microscope. The examined fish were found to be 
infected with Tylodelphys sp., with prevalence of 86%, with the highest 
prevalence shown to be in summer (26%) and the lowest in winter (16%). 
Morphologically, by light and scanning electron microscopy, the parasite 
was found to be linguiform, where the fore body comprised most of the 
worm and the hind body was reduced to a small, conical, pointed end. The 
tegument was unarmed and smooth. A small oral and a large ventral 
sucker were detected. The body contained two types of papillae; a fine 
anterior and a coarse posterior one. The genetic analysis of Tylodephys
sp. showed it was similar to those of the species of fish origin found in 
GenBank, and a description of a new Egyptian genotype (accession 
number MH367017) was provided. The morphotype detected was found to 
have about 99% genetic similarity in the 12S rRNA region with other 
helminthes. The obtained results support an evolutionary addition of the 
Egyptian species of Tylodelphys sp. aiding in its taxonomy and diagnosis.