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

Abstract

Quantitative samples of sediment for the study of the meiofau‐na were collected monthly beweenMar1996 andFeb1997 from a 7‐m‐deep site in the Meloria Shoals, Livorno Italy. In the Tuscan Shoals, 16 species of tardigrades were found belonging to the families Stygarctidae, Halechiniscidae, and Batillipedidae. Megastygarctides orbiculatus and Actinarctus doryphorus are reported for the first time in the Mediterranean Sea, and a re‐description of Batillipes similis is proposed. Global density of the Tardigrada population fluctuated between 8 ind./10 cm² in May 1996 and 285 ind./10 cm² in January 1997. The lowest value of the Shannon‐Wiener biodiversity index (H’ = 1.09) was found in September 1996, whereas the highest score (H’ = 2.46) was obtained inMar1996. Pielou's evenness index (J) fluctuated between 0.40 and 0.88, values attained in January 1997 andMar1996, respectively. The study confirms the notion that the organogenic detritus of the Shoals represents a very favourable environment for meiofaunal organisms in general, and Tardigrada in particular.

Key words:

• Tardigrada
• Mediterranean Meiofauna
• Benthos
• Biodiversity
• Population dynamics