Freshwater and limno-terrestrial meiofauna of the Massane Forest Reserve in the Eastern French Pyrenees

We report the results of a faunistic survey focused on freshwater and limno-terrestrial meiofauna to improve biodiversity knowledge in a protected area in the Eastern part of the French Pyrénées: the Massane Forest Reserve (336 Ha). The survey provided 1187 occurrence records from 315 taxa (most resoved at species-level), uploaded as a shared online dataset. The dataset of freshwater and limno-terrestrial meiofauna from the Massane Reserve and surrounding areas was built starting from 150 samples collected during several survey in the area between 2021 and 2023, covering diverse organismic groups from different habitats. The highest number of occurrences and distinguishable morpho-taxon belong to the group Nematoda (775 occurrences, 172 taxa), followed by Rotifera (219 occurrences, 67 taxa), Platyhelminthes (85 occurrences, 32 taxa), Tardigrada (69 occurrences, 25 taxa), and Gastrotricha (39 occurrences, 19 taxa). A diversity of meiofaunal organisms was found, in large numbers, in all the samples screened: from stream biofilms and sediments, to forest floor soils, mosses, and litter, to a broad range of tree-related micro-habitats associated with beech-like epixylic mosses and lichens, tree cavities, woodpecker breeding holes, bark pockets and fruiting bodies of saproxylic fungi. The dataset includes 1187 occurence records of 315 distinct taxa of meiofauna collected at the Massane Forest Reserve: 219 taxa have been diagnosed at species-level, 75 at genus-level and 21 at family-level. Of the taxa reported in the current dataset, 41 (13%) are Rotifera Bdelloidea (157 occurrences), 26 (8%) are Rotifera Monogononta (62 occurrences), 19 (6%) are Gastrotricha (39 occurrences), 25 (7.9%) are Tardigrada (69 occurrences), 172 (54%) are Nematoda (775 occurrences) and 32 (10%) are Platyhelminths-microtubellaria (85 occurences). The data were structured based on the Darwin Core standard (Wieczorek et al., 2012). This survey makes the Massane forest one of the few protected areas of the world with a taxa-inclusive meiofauna dataset, which could serve as a standard inventory to further consider micro-invertebrates in forest conservation.