ABSTRACT
Meiofauna is a guild of microscopic organisms (delimited by the mesh width of two sieves, upper 500 μm and lower 44 μm) that inhabit the sediment grains and periphyton of aquatic environments (both freshwater and marine). Despite the fact that this definition is based on size, all the environments inhabited by these microorganisms present similar ecological challenges, which suggests that the meiofauna is a biologically and ecologically independent entity. Currently, meiofaunal organisms are represented in 23 of the 34 known metazoan phyla, including Tardigrada, Gastrotricha, and Kinorhyncha. The goal of this study was to compile information on the diversity and distribution of these phyla in Brazil. Based on the taxonomic contributions published until July 2023, a total of 97 Tardigrada species, 88 Gastrotricha species, and five Kinorhyncha species have been recorded. They are distributed throughout five biomes, eight hydrographic regions, 10 terrestrial biogeographic provinces, three marine biogeographical provinces, and 15 political states in Brazil. The species accumulation curve suggests that there are still many Tardigrada and Gastrotricha species to be discovered with increasing sampling effort, as the rate of discovery of new species is linearly increasing. Unfortunately, knowledge of the biodiversity of these meiofaunal groups is still limited due to sparse information on identity and distribution. We recommend future studies dealing with meiofauna taxa to prioritize redescribing endemic species based on integrative taxonomy and increase the number of the type series deposited in Zoological Museums (e.g., specimen photos). Furthermore, the training of researchers specialized in these taxa is a priority, as some of these phyla do not have any Brazilian specialists.
KEY WORDS:
Biodiversity; endemic species; less-known taxon; Linnean shortfall; microinvertebrate; taxonomy
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