Analysis of the tegument of Zygocotyle lunata (Trematoda: Paramphistomidae) adults by scanning electron microscopy.

Paramphistomiasis is a parasitic disease caused by various species of the Paramphistomidae. These species mainly affect domestic and wild ruminants; the economic impact of these diseases is often underestimated. Traditionally, the identification of paramphistomes has been difficult and has been based on morphological aspects such as the body shape, the position of the esophagus and cecae, or the tegumental papillae. Despite the many investigations regarding the tegumental papillae for other paramphistomes, very few efforts have been made using Zygocotyle lunata, partly because many authors differ with respect to the importance of papillae in the classification of paramphistomids. Herein, we characterize by scanning electron microscopy new tegumental papillae not previously described on the tegument of 3-wk-old Z. lunata adults obtained from mice. Three morphologically different papillae (rosette, ciliated, and conical papillae) were observed and are described. Based on these results, we assert that the newly recognized morphological features should be used for species differentiation in the future in addition to the new molecular techniques.