The first record of amphibians as paratenic hosts of Serpinema larvae (Nematoda; Camallanidae).

Until now the third-stage larvae of Serpinema trispinosum (Leidy, 1852) was only found infecting aquatic snail and planktonophagous fish as paratenic hosts (Bartlett and Anderson, 1985; Moravec et al., 1998). The life cycle of this nematode is unknown. Apparently, the freshwater turtles may become infected by ingestion of zooplankton intermediate hosts (e.g., copepods) or by feeding on paratenic hosts (Moravec, 1998). Adults of S. trispinosum are common parasites of freshwater turtles from North and Central America (Baker, 1987; Moravec and Vargas-Vázquez, 1998). Lysapsus limellum Cope, 1862 is a member of the frog family Hylidae. It is distributed exclusively in South America, in Uruguay, Paraguay, Bolivia and the north of Argentina (Frost, 2004). In Argentina, L. limellum is restricted to some areas adjacent to the Paraguay and Paraná rivers. It shows a great preference for aquatic habitats and occurs in permanent and semipermanent ponds. Studies on the parasite fauna of L. limellum from Corrientes, Argentina showed the presence of thirty three nematode larvae of the family Camallanidae. Specimens were identified as third-stage of Serpinema cf. trispinosum. Forty three amphibians were collected in a pond located 15 km from Corrientes City (27° 28’ S and 58° 50’ W), province of Corrientes, Argentina between December, 2000 and January, 2001. They were captured with a 45 cm diameter dip net. Nematodes were recovered from the intestine, killed and fixed in hot water (80° C), stored in 70° ethyl alcohol and cleared in lactophenol for further examination. Drawings and measurements were made with the aid of a Zeiss microscope with a lucida camera. Measurements are given in micrometers (μm) as the minimum-maximum, followed by the mean ± standard deviation in parentheses. Morphology (Figures 1-4) Based on 11 specimens. Nematodes with colourless body and almost smooth cuticle, 1170.0-1930.0 (1666.0 ± 226.0) long by 46.0-80.0 (57.0 ± 11.0) wide. Cephalic end with 8 small papillae and lateral amphids. Buccal capsule is of the “Paracamallanus” type. Anterior portion 37.0 42.5 (40.09 ± 1.84) long by 25.3 43.0 (31.0 ± 6.0) wide, formed by two wide, lateral, valve-like structures with ribs at the inner side. This portion of capsule has 15 narrow, long, longitudinal ridges extending approximately along anterior two thirds of this portion, and 2-4 short ridges. Posterior portion of the buccal capsule is narrower, 16.0-22.0 (20.0 ± 1.70) long by 13.8 29.0 (20.0 ± 4.0) wide. This portion opens into the esophagus through a large funnel with sclerotized walls. The esophagus consists of two portions: muscular esophagus 197.8 305.0 (227.0 ± 31.0) long by 25.3 40.0 (29.0 ± 4.0) wide and glandular esophagus 184.0 275.0 (201.0 ± 27.0) long by 25.3 40.0 (32.0 ± 4.0) wide. Two large cellular nuclei present close to the 1 2