New dicrocoeliid digeneans from mammals in Ecuador including a highly genetically divergent new genus from an ancient marsupial lineage.

The Dicrocoeliidae is a highly diverse and broadly distributed family of digeneans typically parasitic in the gall bladder and liver of their tetrapod hosts. So far, no study has reported dicrocoeliids, or any digeneans, from the ancient marsupial family Caenolestidae. Herein, we describe a new genus of dicrocoeliids (Otongatrema n. gen.) from Tate's shrew opossum Caenolestes fuliginosus and a new species of Metadelphis (Metadelphis cesartapiai n. sp.) from a phyllostomid bat Anoura peruana collected in Ecuador. Otongatrema can be readily distinguished from the morphologically closest dicrocoeliid genera Concinnum, Conspicuum and Canaania based on the position of the genital pore, distribution/position of the uterus and extent of vitellarium. Metadelphis cesartapiai can be easily differentiated from other Metadelphis spp. based on a combination of morphological characters including body shape and size, distribution of vitellarium, shape of the gonads as well as size of suckers and cirrus sac. In addition, we used newly generated partial sequences of the nuclear 28S rRNA gene and mitochondrial cox1 genes to examine phylogenetic affinities of the new taxa within the Dicrocoeliidae. Both the 28S and cox1 phylogenies confidently positioned Otongatrema as a sister/basal group to all other dicrocoeliids sequenced so far. The phylogenetic position of Otongatrema may be explained by a close co-evolutionary relationship with Caenolestidae, one of the most basal and most ancient groups of marsupials. In addition, our 28S phylogeny provides evidence that the complete or partial loss of intestinal structures has likely occurred independently at least 3 times in the evolutionary history of the Dicrocoeliidae.