Seek and describe: An integrative description of a new species of Ornamentula (Gastrotricha: Paucitubulatina)

Most gastrotrichs are obligate benthic or periphytic organisms, typically associated with sediment and aquatic vegetation; however, some exceptions exhibit a semiplanktonic lifestyle, such as members of the genus Ornamentula Kisielewski, 1991 (family Dasydytidae Daday, 1905). Here, we describe the third species of the genus, discovered in a lake in southeastern Brazil, using an integrative taxonomy approach. Our description is based on morphological data obtained through optical microscopy and the first high-resolution electron microscope imagery of Ornamentula species, as well as genetic data from nuclear ribosomal 18S and 28S loci and mitochondrial COI. Ornamentula sanctipetri sp. nov. differs from its congeners by the presence of asymmetrical dorsal scales, longer cephalic ciliation, an additional third transverse row of scales on the dorsal neck, and additional scales in the ventral trunk interciliary region. Molecular evidence supports the monophyly of the genus, although Dasydytidae is non monophyletic as presently constituted because Neogosseidae nested within it. An updated identification key for the Ornamentula genus is provided to facilitate future research.