Abstract
Parapharyngodon (Oxyurida) is a lizard gastrointestinal nematode parasite with a life cycle including lizards as main hosts. However, some species are known to parasitize anurans. In the present study, P. japonicus isolated from the large intestine of the Egyptian changeable lizard, Agama mutabilis was described and illustrated. Forty five specimens of these animals were collected from south Sinai desert, Egypt during the period from May to September 2017. After necropsy, the body was opened by a longitudinal incision from vent to throat, and the gastrointestinal tract was removed. The esophagus, stomach, small and large intestines were examined separately for helminthes. The recovered nematodes were examined by light and scanning electron microscopy. Thirty six specimens (80.0 %) were found to be naturally infected. The parasite was robust with prominent cuticular transverse annulations. Mouth surrounded by three bilobed lips, each with tiny labial papillae. Three pairs of caudal papillae were observed in male worms; 1 pair precloacal, 1 pair sublateral in cloacal opening line, 1 pair in proximal region of caudal appendage on its narrowed point. The posterior extremity beard dorsally directed caudal appendages. Females were with a conical posterior end terminated at a terminal spike. Ovaries reached esophageal isthmus but not wrapped around corpus. The parasite recorded was compared morphologically and morphometrically with the most similar species, it was found that it was most similar to P. japonicus with new host and locality records.