Abstract
In this paper a new tardigrade species, Macrobiotus azzunae sp. nov., from Tunisia, is described. An integrative taxonomic approach was applied by combining morphological, morphometric and molecular data. In particular, light and scanning electron microscopy observations, and four genetic markers, three nuclear (18S rRNA, 28S rRNA and ITS-2) and one mitochondrial (COI) were used. The analysis showed that M. azzunae sp. nov. belongs to the Macrobiotus hufelandi group and is most similar to Macrobiotus sandrae Bertolani & Rebecchi, 1993. It differs from M. sandrae by a more pronounced constriction of the first macroplacoid (hardly visible in M. sandrae) and for the eggshell shape, with thinner wires of the reticulum and meshes around the processes larger than the inter-process meshes in M. azzunae sp. nov., while all meshes are similar in size in M. sandrae. The species is gonochoristic. With this discovery, there are 33 species of tardigrades identified in Tunisia, all non-marine. This result, compared with nearby Sicily, where more research has been conducted, indicates that there is a considerable potential for identification of new species. Further research will be most informative if multiple habitats are explored and if carried out with an integrated approach as done in this present work.
Highlights
Tardigrades are hygrophilous micrometazoans whose outstanding resistance enables most of them to inhabit a large variety of habitats from the greatest depths of oceans to the highest mountain peaks, as well as extreme environments such as cryoconite holes
The analysis showed that M. azzunae sp. nov. belongs to the Macrobiotus hufelandi group and is most similar to Macrobiotus sandrae Bertolani & Rebecchi, 1993
It differs from M. sandrae by a more pronounced constriction of the first macroplacoid and for the eggshell shape, with thinner wires of the reticulum and meshes around the processes larger than the inter-process meshes in M. azzunae sp. nov., while all meshes are similar in size in M. sandrae
Summary
Tardigrades are hygrophilous micrometazoans whose outstanding resistance enables most of them to inhabit a large variety of habitats from the greatest depths of oceans to the highest mountain peaks, as well as extreme environments such as cryoconite holes. Much research on the diversity and distribution of tardigrade fauna has been carried out in recent years in various parts of the world, especially considering the terrestrial environment. This has led to a significant increase in the number of known species: 531 in 1983 (Ramazzotti & Maucci 1983), about 960 in 2005 (Guidetti & Bertolani 2005) and more than 1300 species in 2020 (Degma et al 2020). Using phase contrast (PhC) light microscopy (LM), differential interference contrast (DIC) and scanning electron microscopy (SEM), we were able to describe the phenotypic characteristics of the new species whereas the amplification of DNA markers (three nuclear, 18S rRNA, 28S rRNA and ITS-2, and one mitochondrial, COI) provided barcodes for the genetic identification of this new species
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