Abstract During a helminthological survey on freshwater turtles from the Brazilian Amazon, we collected fresh and well-preserved nematodes from the stomach of Podocnemis unifilis Troschel, 1848, that resembled Orientatractis leiperi. The morphology and morphometry of specimens described herein fits those from the original description. We also observed important morphological characters not reported previously or not properly described, and those are reported here for the first time: the structure of the excretory pore (surrounded by radial cuticle striations), structure and position of deirids, phasmids, oral papillae and the presence of a dorsolateral pair of papilla in caudal region. The present work provides a detailed redescription for O. leiperi, 50 years after its original description, adding a new host and locality for this species.

Resumen Durante el análisis helmintológico de tortugas de agua dulce en la Amazonía brasileña, fueron extraídos del estómago de Podocnemis unifilis Troschel, 1848, nemátodos que parecían pertenecer a la especie Orientatractis leiperi; estos ejemplares fueron utilizados para realizar la redescripción de esta especie mediante microscopía óptica y microscopía electrónica de barrido. La morfología y morfometría de los ejemplares analizados en este estudio se ajustaron a la descripción original. Importantes caracteres morfológicos que no fueron considerados previamente o que no fueron descritos adecuadamente, se detallan por primera vez en este trabajo: la estructura del poro excretor (rodeado de estrías radiales cuticulares), estructura y posición de las papilas cervicales, fasmidios y papilas orales, distribución y disposición de las papilas caudales en los machos y la presencia de un par de papilas dorsolaterales en la región caudal. Este trabajo presenta una redescripción detallada de O. leiperi, 50 años después de su descripción original, adicionando un nuevo hospedador y nueva localidad para la misma.

Mesocoelium lanfrediaesp. nov. (Digenea: Mesocoeliidae) inhabits the small intestine of Rhinella marina (Amphibia: Bufonidae) and is described here, with illustrations provided by light, scanning electron microscopy and molecular approachs. M. lanfrediae sp. nov. presents the typical characteristics of the genus, but is morphometrically and morphologically different from the species described previously. The main diagnostic characteristics of M. lanfrediae sp. nov. are (i) seven pairs of regularly-distributed spherical papillae on the oral sucker, (ii) ventral sucker outlined by four pairs of papillae distributed in a uniform pattern and interspersed with numerous spines, which are larger at the posterior margin and (iii) small, rounded tegumentary papillae around the opening of the oral sucker, which are morphologically different from those of the oral sucker itself, some of which are randomly disposed in the ventrolateral tegumentary region of the anterior third of the body. Addionally, based on SSU rDNA, a phylogenetic analysis including Brachycoeliidae and Mesocoeliidae taxa available on GenBank established the close relationship between M. lanfrediae sp. nov. and Mesocoelium sp.