First record of <i>Hydra vulgaris pedunculata</i> (Cnidaria, Hydrozoa) in seasonally flooded Andean grasslands and their role as planktonic predator

Information regarding the distribution and ecology of the genus Hydra in Argentina remains limited, and species-level identifications from Patagonian wetlands are currently unavailable. In this study, dense aggregations of red-colored polyps were observed in two temporary wetlands within Nahuel Huapi National Park. Environmental and limnological variables were characterized at each site, and specimens were identified based on cnidocyte morphology from the tentacles and body column as Hydra vulgaris pedunculata. Polyps were associated with several submerged and emergent macrophytes, particularly Eleocharis melanostachys and Nitella sp. Controlled feeding experiments were conducted using different planktonic prey to evaluate the predatory capacity of Hydra. These experiments revealed high predatory plasticity, with greater consumption of cladocerans and small- to medium-sized chironomid larvae. These findings provide the first species-level identification of Hydra inhabiting northern Patagonian temporary wetlands and contribute to the ecological and taxonomic knowledge of freshwater cnidarians in this region.