Pharyngodon mamillatus (Nematoda: Pharyngodonidae) in the ocellated skink Chalcides ocellatus (Squamata: Scincidae) from Egypt: Light and scanning electron microscopic studies.

Twenty-one Pharyngodon mamillatus were recovered from the large intestine of 4 out of 12 ocellated skink Chalcides ocellatus collected from the South Sinai desert, Egypt. The prevalence of infection was 33.33% (intensity 2-4). The recovered pharyngodonid was re-described based on light and scanning electron microscopy. According to the morphology, it was characterized by regular transverse annulations extending from the posterior margin of the lips to the level of the anus, triangular mouth opening was surrounded by three large bilobed lips possessing three papillae, oval-shaped excretory pore, slit-like vulva opening, and slit-like anal ventral opening at the posterior end which terminates with a tail filament. Here, the morphometric measurements of adult female P. mamillatus were given in this study. It has no intraspecific morphological variations from the previously described P. mamillatus, but it appeared with small range on biometric features. These variations may be accounted by host/environment attributes since they exhibit wide host and geographical spectra. The present study was applied for detailed morphological knowledge of the recovered P. mamillatus for strengthening their taxonomic validity. HIGHLIGHTS: The Pharyngodon mamillatus naturally parasite of the intestinal region of Chalcides ocellatus. The present study clarifies the morphological key for the description of P. mamillatus.