Freshwater planarians are among biology's most startling organisms: flatworms whose abundant adult stem cells, called neoblasts, let them regrow lost body parts and, in some species, reproduce simply by fragmenting. A study in BMC Ecology and Evolution led from the Universidad de Chile now shows the country hosts far more planarian diversity than anyone had recorded, identifying six genetically distinct lineages that may represent species unknown to science.
The sampling, carried out between 2021 and 2025 by doctoral student Andrés Lagos-Basoalto with Miguel Allende, director of the Millennium Institute Centre for Genome Regulation, and Constanza Vásquez-Doorman of Universidad Bernardo O'Higgins, stretched from the Altiplano to the Los Lagos Region. Two candidate species emerged in the high north, one tied to the El Tatio geothermal field and another found around Chungará, Ascotán and the Lauca River, forming an evolutionary group never before recorded in the genus Girardia.
Further lineages appeared in Lake Calafquén, in Los Lagos, and in central Chile, including the artificial lagoon of Santiago's Parque O'Higgins. Before this work, only five freshwater planarian species had been formally described in the whole country. The authors stress these are potential species requiring further evidence, and the centre is now launching an environmental DNA survey to catalogue the group properly.
The stakes go well beyond taxonomy. Planarians are prized models for understanding how tissue can regenerate without forming tumours, and populations adapted to geothermal extremes could point to genes for DNA repair and stress tolerance. Their sensitivity to pollutants also makes them promising bioindicators of water quality, while lineages confined to single habitats become immediate conservation concerns.