The remarkable richness of Girardia (Platyhelminthes: Tricladida) in Brazilian subterranean habitats: Two new species from sandstone and limestone caves

Abstract

The triclads of the suborder Continenticola have little known diversity in freshwater environments in South America, with few studies on their distribution in the Neotropical region. In this article, we describe two new species of Girardia that live in caves and discuss their phylogenetic relationships with the most recent phylogeny of the genus. Girardia patiensis Morais & Leal-Zanchet, sp. nov. and Girardia alba Morais & Leal-Zanchet, sp. nov. are described from a single cave, made of sandstone (Gruta do Castelo) and limestone (Gruna da Pingueira), respectively, located in transition areas between Cerrado and Caatinga in northeastern Brazil. Specimens of both G. patiensis and G. alba have whitish bodies and small auricles. Eyes are small in G. patiensis and absent in G. alba. Both species can be easily differentiated from each other and from their congeners by a combination of characteristics of their copulatory apparatus. Girardia patiensis has a large and irregular, funnel-shaped bulbar cavity with indentations and diverticula and a slightly sloping bursal canal. Girardia alba has a bulbar cavity with asymmetrically bifurcated portions and an angled bursal canal. Phylogenetic inferences based on a combined molecular matrix (concatenating COI + EF1α) indicated that G. patiensis and G. alba form a well-supported clade, closely related to an undescribed, epigean species from Mexico, which constitutes the sister group to the epigean G. schubarti from Southern Brazil. The two new species are categorized as troglobites and are under threat, since Gruta do Castelo (type-locality of G. patiensis) is visited in an uncontrolled manner and the site where they occur is constantly trampled, while Gruna da Pingueira (type-locality of G. alba) has no legal protection (Conservation Unit), and its surroundings are deforested.