Integrative description of a new species of Acanthodasys Remane, 1927 (Gastrotricha, Macrodasyida, Thaumastodermatidae) based on four distinct morphological techniques and molecular data

The number of undescribed animal species is still very high, in particular among the marine meiofaunal taxa. For these invertebrates, external and internal morphological information are often scarce and species delimitation and identification is a real problem. As a contribution to this shortfall, we describe a new gastrotrich species of the genus Acanthodasys (Macrodasyida, Thaumastodermatidae) from sublittoral sediments of the Brazilian southeastern coast based on four distinct morphological techniques (optical microscopy - DIC, CLSM, SEM, TEM) and molecular data. Acanthodasys australis sp. nov. is characterized by spined scales (uniancres) of different sizes and densities on the dorsal and ventral body sides, two types of spineless scales scattered among the spined scales, and 6 TbA per side forming two distinct groups (2 þ 4) each arranged in two transverse rows. A molecular phylogeny of the family Thaumastodermatidae using a multigene approach found Acanthodasys to be monophyletic. This is the first species belonging to the genus Acanthodasys to be described from the Southern Hemisphere.