Surface ultrastructure of the cercaria of Neodiplostomum seoulense (Trematoda: Neodiplostomidae).

The surface ultrastructure of Neodiplostomum seoulense cercariae was studied by scanning electron microscopy. The cercarial body was cylindrical and its tail bifurcated. Short tegumental spines, with a broad base and single pointed tip, were dense anteriorly but sparse posteriorly on the lateral margins of the body. The acetabulum had stout spikelike spines, centripetally oriented on the inner surface. Sensory papillae, each with a short cilium, were concentrated around the oral sucker; they could be tangoreceptors or chemoreceptors, or both. Many sensory papillae, each with a long cilium, were observed on the tail; these might be rheo- or tangoreceptors. It is suggested that the sensory papillae of N. seoulense cercariae provide for attachment and penetration into the skin of tadpoles, which are the second intermediate host.