The present study aims to describe a new genus and species of microphalloid digenean parasite of two species of bats of the genus Peropteryx from the Mexican Neotropics (in the states of Chiapas and Yucatán). Morphological and molecular data (28s rDNA ribosomal gene sequences) were used to study Digeneans. Sagittatrema zutzi gen. nov. sp., nov., is diagnosed morphologically by having a sagittiform body, a genital pore in the midline of the body, posterior to the ventral sucker, and a cirrus sac running through much of the diameter of the ventral sucker. The nine sequences generated from the 28S rDNA gene were used to examine the phylogenetic affinities of this new taxon within the superfamily Microphalloidea Ward, 1901, using Maximum Likelihood and Bayesian Inference analyses. Both analyses resulted in trees with similar topologies and formed a well-supported clade (Bt = 100; pp = 1) with the Sagittatrema sequences. Because of the new genus’s phylogenetic position and that some sister families to the proposed taxa, like Pleurogenidae and Prosthogonimidae, are polyphyletic, we prefer to consider Sagittatrema as a genus incertae sedis within Microphalloidea. A full systematic review of microphalloids is needed to confirm their phylogenetic position.

The phylogenetic position of most xiphidiocercariae from subgroups Cercariae virgulae and Cercariae microcotylae remains unknown or unclear, even at the family level. In this paper, we studied the morphology and molecular phylogeny of 15 microcotylous and virgulate cercariae (11 new and four previously described ones). Based on morphological and molecular data, we suggested five distinct morphological types of xiphidiocercariae, which are a practical alternative to Cercariae virgulae and Cercariae microcotylae subgroups. Four of these types correspond to actual digenean taxa (Microphallidae, Lecithodendriidae, Pleurogenidae and Prosthogonimidae), while the fifth is represented by Cercaria nigrospora Wergun, 1957, which we classified on the basis of molecular data for the first time. We reassessed the relative importance of morphological characters used for the classification of virgulate and microcotylous cercariae, and discussed the main evolutionary trends within xiphidiocercariae. Now stylet cercariae can be reliably placed into several sub-taxa of Microphalloidea on the basis of their morphological features.

Data on the interposition of the immunoreactive nerve cords in Cercaria parvicaudata Stunkard & Shaw, 1931 (Trematoda: Renicolidae) and its chaetotaxy were obtained. The nervous system of C. parvicaudata was described using immunostaining of 5-hydroxytryptamine and FMRFamide immunoreactive nerve elements. The morphology and distribution of sensory receptors were analysed using scanning electron microscopy and the silver nitrate impregnation technique. Our integrated approach to the study of the nervous system revealed a clear colocalization of surface papillae with nerve cords and commissures in C. parvicaudata. The structure of the nervous system in C. parvicaudata differs partly from the classical model that defines the entire nomenclature of chaetotaxy.