First report of Gieysztoria falx Brusa, Damborenea & Noreña, 2003 (Platyhelminthes: Rhabdocoela) in southern Brazil

Abstract

Within Dalyelliidae Graff, 1905, Gieysztoria Ruebush & Hayes, 1939 is the most widely distributed and speciose genus, members of which live in marine, brackish, or freshwater habitats (Van Steenkiste et al., 2012). Gieysztoria is composed by ~97 free-living species (Tyler et al. 2016), and species identification is mainly made on the male copulatory system, which has an armed penis (stylet) with different configurations of spines (Noreña et al., 2016). The stylet configuration of Gieysztoria species is traditionally split into two groups: Aequales (spines of similar shape and size) and Inaequales (spines of different shape and size) (Luther, 1955). In the neotropics, specimens of Gieysztoria belong to both the Aequales and Inaequales group and are well represented (Damborenea et al., 2005; Noreña et al., 2003). According to Braccini et al. (2016, 2017), there are 16 species of Gieysztoria in Brazil, mainly distributed in the southern region. South Brazil harbours a mosaic of wetlands that are considered hot spots of biodiversity, including the Taim Ecological Station (ESEC Taim) protected area that was designated as a Ramsar site (Ramsar, 2017). In the present study, Gieysztoria falx Brusa, Damborenea & Noreña, 2003 is registered in the ESEC Taim, located in Rio Grande do Sul. It represents the first record of G. falx in Brazil. Illustrations and comments on stylet configuration are given.

Species composition and abundance of free-living turbellarians in three different wetlands in Southern Brazil

“…Regarding less dominant species, such as microturbellarians, most of them are widely distributed and well-known. We found a few species that are representatives of the Neotropical region (e.g., Gieysztoria falx, G. duopunctata, G. evelinae, G. hermes, G. hymanae, Stenostomum paraguayense, and Bothromesostoma evelinae) as other authors reported earlier (Martín 1908, Marcus 1946, Brusa et al 2003, Reyes et al 2019, Reyes et al 2021. The abundance of microturbellarians in the neotropics depends mainly on the life cycle and flooding (Noreña-Janssen 1995).…”

“…Species rarefaction curves for each site were built based on the accumulation of individuals (abundance) (Colwell & Elsensohn 2014), so that biases in comparisons due to differences in the abundance of some turbellarians species were corrected (Gotelli & Colwell 2001). Because the ESEC Taim has few previously published records of turbellarian species (Reyes et al 2019, Reyes et al 2021, we tested the performance of five non-parametric richness estimators, based on abundance (Chao 1) and incidence (Chao 2, Jacknife 1, Jacknife 2, and Bootstrap), to determine the completeness of the species inventory. Hence, richness estimators were used to understand the alpha diversity in each sampling site and considering the ESEC Taim as a whole (14 samples).…”