Italian Kinorhyncha: status of biodiversity and distribution

Kinorhyncha are microscopic marine metazoans constituting a phylum that comprises more than 250 described species living from intertidal to abyssal depths. Studies on the Italian kinorhynch fauna have been rather erratic in space and time, with most records originating in the first decades of the XX century from the Gulfs of Naples and Trieste. Here, we provide information based on a careful taxonomic revision of published material but mainly on new data from recent surveys carried out in areas of Ligurian Sea (4), Tyrrhenian Sea (8), Ionian Sea (1), and Adriatic Sea (3 localities). New data derives from qualitative as well as from quantitative samples. During our surveys, 30 species in 11 genera and 6 families were recorded. Of the species found, 16 appear new to science or new to the national fauna, while 14 were previously known from Italian waters. Particularly relevant is the finding of two new species of the rare genus Condyloderes, unreported before from the Mediterranean Sea. The new faunistic information, along with novelties in the systematics of the phylum, prompted us to prepare an updated checklist, which brings to 37 species, 11 genera and 6 families the number of kinorhynch taxa known from the Italian seas. The most speciose genus is Echinoderes, followed by Pycnophyes, with 11 and 10 species, respectively. The former genus includes the species showing the highest abundances, E. capitatus, with recorded densities up to 184 ind./10 cm2, while the latter includes the most common species P. communis, found in 12 localities from the Ligurian, Tyrrhenian, and Adriatic Seas. Concerning distribution, it appears that five species only can be considered ubiquitous in the four Italian sea basins, whereas the other species seem to be restricted to one or two basins. However, many sectors of the national waters remain unexplored. Further research should concentrate especially on peculiar habitats, such as coarse biogenic sediments, submarine caves, and lagoons, which our studies indicated as biodiversity hotspots for the ‘mud dragons’