Diversity of the water bears (Tardigrada) in Ethiopian Soil

Tardigrades are microscopic invertebrates inhabiting a wide range of marine, freshwater, and terrestrial environments. Although tardigrades are widely distributed, knowledge on their diversity remains geographically uneven, and most of the African continent is still poorly studied. This knowledge gap particularly includes soil tardigrades, which are poorly known in comparison to those inhabiting mosses and lichens. Moreover, high heterogeneity of soil combined with limited standardization and replication of previous studies has prevented reliable comparisons of soil tardigrades diversity and distribution. Given Africa’s significant climatic, topographic, and habitat diversity, the continent may be host to a rich and largely undocumented tardigrade fauna.

Ethiopia encompasses parts of two global biodiversity hotspots (the East Afromontane and the Horn of Africa) with the continent’s largest Afroalpine region. Natural habitats of the country range from tropical and Afromontane forests to high-altitude Afroalpine lands, offering a wide variety of microhabitats for limno-terrestrial tardigrades. However, up to present only nine tardigrade taxa have been reported from Ethiopia.

To address this significant knowledge gap, 93 soil samples, collected in six geographically and ecologically distinct regions of Ethiopia, were examined. Using an integrative taxonomic approach that combines morphological, morphometric, and molecular data, the study aimed to document the country’s soil tardigrades diversity.

In summary, tardigrades were found in 26 samples (only ca.28% of examined samples). In total, 101 individuals and 77 eggs were found. Although, low density the diversity of tardigrades was very high. In total, 15 genera i.e. Acutuncus, Bertolanius, Calcarobiotus, Hypsibius, Isohypsibius, Itaquascon, Macrobiotus, Mesobiotus, Necopinatum, Paraisohypsibius, Paramacrobiotus, Parhexapodibius, Pilatobius, Ursulinius and Xanthobiotus were identified. Among them, one genera and two species of Pilatobius and Ursulinius new to science have been discovered. The taxonomic positions of these new taxa were supported by an evaluation of detailed morphological and morphometric traits combined with molecular analyses based on four genetic markers: 18S rRNA, 28S rRNA, ITS-2, and COI.