Surface ultrastructure of the adult and juvenile stages of the trematode Astiotrema impletum (Looss, 1899) Looss 1900 (incertae sedis) from the Nile puffer, Tetraodon lineatus Linnaeus, 1758

A scanning electron microscope study was performed on the surface of the trematode Astiotrema impletum (Looss, 1899) Looss 1900 from the Nile puffer, Tetraodon lineatus Linnaeus, 1758 (Syn. Tetraodon fahaka) for the first time. Adult A. impletum have a markedly large, sub-terminal oral sucker and a small ventral sucker. As with most trematodes, tegumental spines are concentrated anteriorly and are absent just anterior the ventral sucker. Spines have serrated tips on a short, tongue–shaped body. At the level of the ventral sucker the base of each spine exhibits a three bulbous-like structure that can be partially or completely withdrawn into the tegument. Sensory papillae are concentrated around the oral and ventral suckers and genital pores. Papillae are conical or knob-like, either ciliated or non-ciliated; some are protruded and others are embedded inside the tegument. In the juvenile stage, spines are smaller, less well-developed and tightly packed. The cytoplasmic processes of the posterior quarter of body show brain-like velvety appearance on the adult and small cobblestone-like on the juvenile.