When anatomy speaks louder than genes: two new freshwater planarian species (Platyhelminthes: Dugesiidae) from Argentine Patagonia

Abstract

The Dugesiidae is a family of freshwater planarians (Platyhelminthes: Tricladida), which includes 15 genera, with about 250 valid species. In particular, the genus Girardia encompasses 59 species, mainly distributed in the Neotropics. In this paper, we describe two new species of the genus Girardia, viz. Girardia limayana Negrete & Brusa sp. nov. and Girardia ventriphalla Negrete & Brusa sp. nov., found in different water bodies from Argentine Patagonia. We also studied specimens of Girardia tomasi, which allowed expanding its geographic distribution. The description of the new taxa focuses on their internal anatomy, mainly related to the copulatory apparatus, which was studied by serial histological sections. Partial sequences of mitochondrial cytochrome oxidase subunit I (Cox-1) were also obtained to describe the freshwater planarians within a taxonomic integrative approach, including species delimitation approaches (ASAP and mPTP). The mPTP method recovered the three species herein studied, but ASAP, in its best score, failed to delimit G. ventriphalla sp. nov. from G. tomasi. Considering these approaches, along with the anatomical analyses, we decided to keep these latter species as different entities.