Ciliate biodiversity and preliminary behavioral observations from the chemoautotrophic cave ecosystem of Frasassi, Italy.

Chemoautotrophic cave organisms requires specific adaptations to tolerate the stress of living in darkness and extreme environmental conditions, such as nutrient and energy limitations, low temperatures (12-13°C), highly variable sulphide concentrations (from 0 up to 415 μM H2S), toxic levels of gases (H2S, CO2, CH4), lethally low oxygen concentrations and variable hydrogen ion concentrations. Up to now, very few study attempted to describe ciliate communities from caves as well as, their fluctuation with respect to environmental factors. The aim of the study was to identify, spatio-temporal characterize and observe the behavioural differences of ciliate species from the Frasassi caves. Four sampling locations within Frasassi caves were selected these include Pozzo dei Cristalli, Lago Verde, Ramo Solfureo and Grotta Solfureo. Sampling site Pozzo dei Cristalli was studied in detail for spatio-temporal distribution, since it is highly diversified and include several microhabitats represented by small sulfidic (H2S-rich) ponds, streams and spring as well as, deep and shallow muddy, stagnant lakes. Periodic sampling was realised from 2009 to 2011 in the form of water-sediments, picked up by scraping the surface. Classical culturing, silver staining methods and 18S rRNA gene (for some selected species) for phylogenetic analysis were employed. A total of 31 species were identified belonging to 9 classes, 15 orders and 23 genera. The different ciliate communities were recorded from Pozzo dei Cristalli during various sampling occasions, this could be due to changing environmental conditions, which leads to shifting of ciliate species, those unable to encyst, to a favourable environment within these microhabitats. It was observed that some species e.g. Urocentrum turbo, Coleps hirtus hirtus, Oxytricha sp, Euplotes sp, showed adaptation for the cave environment (Photo-sensitivity, sulphur tolerance, feeding behaviour, morphological difference). The results provide a platform for various in-depth studies of ciliates to understand potential role in ecosystem functioning, nature of chemical compounds secreted, dispersal pattern, adaptations within cave.