Diversity and dynamics of an interstitial Tardigrada population in the Meloria Shoals, Liguria Sea, with a redescription of Batellipes similis (Heterotardigrada, Batillipedidae)

Quantitative samples of sediment for tbc study of the meiofauna were collected monthly beween March 1996 and February 1997 from a 7-m-deep site in tbc Meloria Shoals, Livorno Italy. In tbc Tuscan Shoals, 16 species of tardigrades were found belonging to tbc families Stygarctidae, Halechiniscidae, and Batillipedidac. Megastygarctides orbiculatus and Actinarctus doryPborus are reported for tbc first time in tbc Mediterranean Sea, and a redescription of Batillipes similis is proposed. Global density of . tbc Tardigrada population fluctuated between 8 ind./10 cm2 in May 1996 and 285 ind./10 cm2 in January 1997. The lowest valite of tbc Shannon-Wiener biodiversity index (H' = 1.09) was found in September 1996, whereas the highest score (H' = 2.46) was obtamed in March 1996. Pielou's evenness index (J) fluctuated between 0.40 and 0.88, values attamed in January 1997 and March 1996, respectively. The study confirms the notion that tbc organogenic detritus of the Shoals represents a very favourable environment for meiofauna) organisms in generai, and Tardigrada in particular.