Population and reproductive patterns of the Neotropical planarian Girardia capacivasa (Platyhelminthes, Tricladida), and the influence of seasonality on its life history

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

Free-living turbellarians mostly live in marine and freshwater environments, but they have been little considered in ecological studies. The coastal plain in southern Brazil harbors a diverse fauna and flora, but only a few studies have related environmental factors to the abundance, richness, and distribution of turbellarians. Hence, we analyzed the structure of turbellarian communities in floating vegetation in three differently sized limnic environments. We aimed to determine differences in abundance, density, and richness of turbellarians among these habitats in relation to environmental factors. We found 1,225 turbellarians (34 species) distributed among 6 taxa. The most abundant was Tricladida with 49.4% relative abundance; the remaining (Catenulida, Dalytyphloplanida, Macrostomorpha, Kalyptorhynchia, and Prorhynchida) were less abundant. We found no significant differences among population parameters and environments. Small shallow lakes are a potentially rich environment, while water channels are the richest environment. Larger shallow lakes are not very diverse for turbellarians. Similarities regarding turbellarian communities among close limnic systems could be explained by the connectivity of bodies of water that presents similar aquatic macrophytes and hydrological subsystems, while larger shallow lakes have a different community because they have their own contributing basin and could be influenced by other factors.

Exploring microbial diversity and ecological function of epiphytic and surface sediment biofilm communities in a shallow tropical lake

Microbial communities in epiphytic biofilms and surface sediments play a vital role in the biogeochemical cycles of the major chemical elements in freshwater. However, little is known about the diversity, composition, and ecological functions of microbial communities in shallow tropical lakes dominated by aquatic macrophytes. In this study, epiphytic bacterial and eukaryotic biofilm communities on submerged and floating macrophytes and surface sediments were investigated in Lake Rumira, Rwanda in August and November 2019. High-throughput sequencing data revealed that members of the phyla, including Firmicutes, Proteobacteria, Cyanobacteria, Actinobacteria, Chloroflexi, Bacteriodetes, Verrumicrobia, and Myxomycota, dominated bacterial communities, while the microeukaryotic communities were dominated by Unclassified (uncl) SAR(Stramenopiles, Alveolata, Rhizaria), Rotifers, Ascomycota, Gastrotricha, Platyhelminthes, Chloroplastida, and Arthropoda. Interestingly, the eukaryotic OTUs (operational taxonomic units) number and Shannon indices were significantly higher in sediments and epiphytic biofilms on Eicchornia crassipes than Ceratophyllum demersum (p < 0.05), while no differences were observed in bacterial OTUs number and Shannon values among substrates. Redundancy analysis (RDA) showed that water temperature, pH, dissolved oxygen (DO), total nitrogen (TN), and electrical conductivity (EC) were the most important abiotic factors closely related to the microbial community on C. demersum and E. crassipes. Furthermore, co-occurrence networks analysis (|r| > 0.7, p < 0.05) and functional prediction revealed more complex interactions among microbes on C. demersum than on E. crassipes and sediments, and those interactions include cross-feeding, parasitism, symbiosis, and predatism among organisms in biofilms. These results suggested that substrate-type and environmental factors were the strong driving forces of microbial diversity in epiphytic biofilms and surface sediments, thus shedding new insights into microbial community diversity in epiphytic biofilms and surface sediments and its ecological role in tropical lacustrine ecosystems.

Two new freshwater planarian species (Platyhelminthes: Tricladida: Dugesiidae) partially sympatric in Argentinean Patagonia

Girardia Ball, 1974 is the most diverse and widely distributed genus of the family Dugesiidae (Platyhelminthes: Continenticola) in the Neotropical region. Seven out of the 52 species of the genus are known for Argentina. The Somuncurá Plateau is a region in northern Patagonia with several endemic flora and fauna, but little is known about the free-living Platyhelminthes. We describe two new species of Girardia partially inhabiting in sympatry in the Somuncurá Plateau: Girardia somuncura sp. nov. and Girardia tomasi sp. nov. The identification criteria that we followed was an integrative taxonomic approach based on morphological and molecular data. Thus, we used anatomical features focused on the reproductive system, together with a phylogenetic analysis, using a mitochondrial (COI barcode region) genetic marker. This study is the first phylogenetic analysis of the genus Girardia in which we include the southernmost representatives of America here described, thus making it possible to incorporate them in global phylogenies.