Overcoming linear and wallacean shortfalls in neglected meiofaunal taxa: an integrated view on biodiversity of the phyla Gastrotricha and Tardigrada

• Grant number: 23/05724-9
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants
• Start date: July 01, 2024
• End date: June 30, 2026
• Field of knowledge: Biological Sciences - Zoology - Taxonomy of Recent Groups
• Principal Investigator: André Rinaldo Senna Garraffoni
• Grantee: André Rinaldo Senna Garraffoni
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated scholarship(s): 25/07649-0 - Redescription of Tardigrades from Campos do Jordão Described Between 1930 and 1950: Integrative Taxonomy and Neotype Designation for Species Originally Described by Dr. Rosina de Barros, BP.IC

Abstract

Meiofauna is a guild of microscopic organisms (delimited by the mesh of two sieves, upper 500 ¼m and lower 44 ¼m) that inhabit the sediment grains and periphyton of terrestrial and aquatic environments (both freshwater and marine). Despite that this term is an operational definition, the common environment inhabited by these microorganisms presents specific ecological challenges that allow the meiofauna to be considered as a biologically and ecologically independent entity. Currently, meiofaunal organisms are found in 23 of the 34 known metazoan phyla, among them Gastrotricha and Tardigrada. Unfortunately, the biodiversity knowledge thes meiofaunal groups is limited due to deficiencies in identity and distribution. The discrepancy between the number of described species and the number of existing species is called the Linnean shortfall. This deficiency can be especially severe in meiofauna, since the number of works that aim to discover new species is insignificant, when we compare animals with microscopic body size to those with macroscopic size. The relationship between the lack of information related to the geographic distribution of the species, or problems of sampling effort and the number of scientists due to geographic and accessibility issues is called the Wallacean shortfall. It is interesting to note that both deficiencies give rise to a particular meiofauna problem known as the "meiofauna paradox". The scarce taxonomic knowledge of the species results in an imprecise delimitation and identification of the species, as they have ubiquitous distributions, which is paradoxical for meiofaunal small benthic organisms with a short life cycle and non-existent larval stage. This project aims to expand the collection points of gastrotrichs and tardigrades in Brazil, using an integrative approach with morphology techniques (light microscopy with differential interference contrast, scanning electron microscopy, transmission electron microscopy and confocal) and molecular investigation looking forward to solving the problems of species delimitation, studies of morphological characters, increase in the number of deposits of reference material in museums, providing the expansion of knowledge about the distribution, diversity and classification of these tiny animals. (AU)