Publication Date:
2010-10-13
Description:
Benthic foraminifera are an important component of the marine living biota, but protocols for investigating their viability and metabolism are still extremely limited. Classical studies on benthic foraminifera have been based on direct counting under light microscopy. Typically these organisms are stained with Rose Bengal, which binds proteins and other macromolecules, but this approach does not allow discriminating between viable and recently dead organisms. The fluorescent in situ hybridization technique (FISH) represents a potentially useful approach identifying living cells with active metabolism cells. In this work, we tested for the first time the suitability of the FISH technique based on fluorescent probes targeting the 18S rRNA, to detect these live benthic protists. The protocol was applied on the genus Ammonia, on the Miliolidae group and an attempt was made also with agglutinated species (i.e., Leptohalysis scottii and Eggerella scabra). In addition microscopic analysis of the cytoplasm colour, presence of pigments and, sometimes, those of pseudopodial activity where conducted. The results of the present study indicate that FISH targeted only live and metabolically active foraminifera. These results allowed to identify as "live", cells improperly classified as "dead" by means of the classical technique (Type I error) and vice versa to identify as dead the foraminifera without rRNA, but stained using Rose Bengal (Type II error). In addition, the comparative FISH analysis of starved and actively growing cells demonstrated that individuals with active metabolism were stained more intensively than starved cells. This finding supports the hypothesis that the physiological status of cells can be directly related with the intensity of the fluorescent signal emitted by the fluorescent probe. We conclude that the use of molecular approaches could represent a key tool for acquiring crucial information on living foraminifera specimens and for investigating their ecological role in marine sediments.
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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