Abstract: Aplectana hylambatis is a nematode with a wide geographic distribution and low host specificity. In spite of numerous reports, until this moment, the morphological variations between different hosts and localities have not been studied. We studied 401 specimens collected from five host species from seven localities in Argentina, and examined the following morphological characters: mamelon-like cuticular protuberances anterior to the vulva, structure of the gubernaculum and the spicules, number and arrangement of caudal papillae, and the measurements of twelve characters in females and eleven characters in males. The results showed that mamelon-like protuberances and caudal papillae varied in number and arrangement between different hosts and localities. The metrical study revealed that five characters in males and six in females contributed to variability; nine characters showed significant differences between host species and localities. Specimens of A. hylambatis collected from R. arenarum formed a group clearly differentiated from the rest of the specimens. The results from this study highlight the importance of examining as many specimens as possible from different host samples and from several localities to cover the intraspecific variations.

Abstract: The goal of the present study was to analyze the metacercariae found in adult amphibians collected in the Argentinean Chaco region. A total of 194 frogs, Leptodactylus chaquensis, Leptodactylus latinasus, and Lepidobatrachus laevis was examined for digeneans. Three different larval trematodes of the genus Strigea (Digenea, Strigeidae) were found infecting the liver, mesentery, body cavity, and muscle of frogs. These metacercariae are described and illustrated for the first time and provide new information on the composition of metacercariae in amphibians, thus contributing to the knowledge of larval trematodes biodiversity in the Neotropical region. We also present new information on the morphology and morphometry of strigeid metacercariae.