Molecular and New Morphological Data on Nematode Hedruris dratini Found Parasitizing Pseudis minuta (Anura: Hylidae)

Hedruris has a worldwide distribution, parasitizing lampreys, fishes, frogs, and lizards. In South America, 4 species have been reported on frogs (Hedruris heyeri, Hedruris juninensis, Hedruris moniezi, and Hedruris mucronifer), 3 on fishes (Hedruris basilichtensis, Hedruris orestiae, and Hedruris suttonae), and 1 on turtles (Hedruris dratini). We examined a frog (Pseudis minuta) found dead in the Pescado stream, Argentina, searching for parasites. A Hedruris sp. was found and subsequently subjected to integrative analyses. The 18S rDNA was sequenced, and specimens were examined using electron and optical microscopy. Genetic analysis grouped this nematode with H. dratini. Its morphology was similar to that species but differed in having bifid derid in frogs, compared to a simple deirid in turtles. This difference could result from various causes, such as host-parasite interaction or a teratological feature, or it could indicate high morphological variability. To resolve this, molecular analysis of all described Hedruris species is necessary, in addition to morphological studies. According to the prevalence and intensity of infection reported in the literature, the definitive host of H. dratini is likely the turtle. However, the nematode may use different hosts, or the frog may have ingested an amphipod harboring the parasite's intermediate stage. This is the first Hedruris parasite of frogs to be sequenced and represents, after H. mucronifer, the second report of the genus in anurans from Argentina.