Further studies on the marine tardigrade fauna from Sardinia (Italy)

An investigation on the taxonomy and ecology of marine tardigrades was carried out in different intertidal and subtidal sites along the coasts of Sardinia (Italy). Particle size analysis of sediments revealed medium or medium-fine intertidal sands and coarse subtidal sands, the latter mainly formed by coralligenous debris. The systematic study was particularly relevant, leading to the identification of 25 species, of which 9 are new records for Sardinia, and 2 are new to science. With these new findings, the total number of species for Sardinia adds up to 47. The species found belong to the families Halechiniscidae (16 species; abundance 2 to 263 ind. 10 cm-2), Batillipedidae (6 species; abundance 2 to 574 ind. 10 cm-2) and Stygarctidae (3 species; abundance 0 to 13 ind. 10 cm-2). The present data confirm the existence of a remarkable diversity, both of intertidal and subtidal tardigrade fauna. Generally, the prevalently siliceous intertidal sands host a few number of species (sometimes with many individuals), while the subtidal sediments, which were mainly calcareous, show a higher number of species often with low density. In fact, in the intertidal sediments only 11 species were found, 5 belonging to Halechiniscidae and 6 to Batillipedidae. In the subtidal sediments, there was a much wider variety; Halechiniscidae showed the highest number of species (16), compared to the remaining families, while Stygarctidae, which were present only in subtidal sediments, accounted only for 3 species. In the intertidal zone the highest value of the diversity index (H') was 2.1 and in the subtidal zone it was 3.3.