Two new species of the genus Milnesium Doyère, 1840 (Tardigrada, Apochela, Milnesiidae) from Madagascar

Abstract

The knowledge of the diversity and distribution of tardigrades on Madagascar is rather poor. To date, only 13 tardigrade taxa have been reported from this region (including one <i>Milnesium</i> species). We examined 46 specimens belonging to two new-to-science species of the genus <i>Milnesium</i> described herein using an integrative approach, including classical morphology and molecular marker (COI, ITS-2 and 28S rRNA) analysis. The species were found in two moss and lichen samples collected in the Ivohibory forest in Fianarantsoa Province. <i>Milnesium matheusi</i> <b>sp. nov.</b>, with claw configuration [3-3]-[3-3] and rather wide buccal tube, morphologically is most similar to: <i>Mil. beatae</i> Roszkowska, Ostrowska & Kaczmarek, 2015, <i>Mil. bohleberi</i> Bartels, Nelson, Kaczmarek & Michalczyk, 2014, <i>Mil. eurystomum</i> Maucci, 1991, <i>Mil. shilohae</i> Meyer, 2015 and <i>Mil. tumanovi</i> Pilato, Sabella & Lisi, 2016; however, it differs from these by morphometric characteristics. <i>Milnesium wrightae</i> <b>sp. nov.</b>, by the presence of four points on secondary branches of claws IV, is most similar to <i>Mil. quadrifidum</i> Nederström, 1919. However, <i>Mil. wrightae</i> <b>sp. nov.</b> differs from <i>Mil. quadrifidum</i> by claw configuration ([4-4]-[4-4] in <i>Mil. quadrifidum</i> vs. [3-3]-[4-4] in <i>Mil. wrightae</i> <b>sp. nov.</b>), but also by the position of the fourth points on secondary branches of claws IV, which are located near the base of the claw in the new species and near the top of the claw in <i>Mil. quadrifidum</i>. Genotypic analysis showed that <i>Mil. matheusi</i> <b>sp. nov.</b> is most similar to <i>Milnesium</i> sp. (28S rRNA), <i>Mil. variefidum</i> (COI) and <i>Mil. t. tardigradum</i> (ITS-2) while <i>Mil. wrightae</i> <b>sp. nov.</b> is most similar to <i>Milnesium</i> sp. (28S rRNA), <i>Mil. variefidum</i> (COI) and <i>Mil. matheusi</i> (ITS-2). Five <i>Milnesium</i> taxa are recorded from the African region, including the two new species from Madagascar reported in this study.