Selective Feeding of Bdelloid Rotifers in River BiofilmsReportar como inadecuado

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In situ pigment contents of biofilm-dwelling bdelloid rotifers of the Garonne River France were measured by high performance liquid chromatography HPLC and compared with pigment composition of surrounding biofilm microphytobenthic communities. Among pigments that were detected in rotifers, the presence of carotenoids fucoxanthin and myxoxanthophyll showed that the rotifers fed on diatoms and cyanobacteria. Unexpectedly, while diatoms strongly dominated microphytobenthic communities in terms of biomass, HPLC results hinted that rotifers selectively ingested benthic filamentous cyanobacteria. In doing so, rotifers could daily remove a substantial fraction up to 28% of this cyanobacterial biomass. The possibility that the rotifers hosted symbiotic myxoxanthophyll-containing cyanobacteria was examined by localisation of chlorophyll fluorescence within rotifers using confocal laser scanning microscopy CLSM. CLSM results showed an even distribution of quasi–circular fluorescent objects FO throughout rotifer bodies, whereas myxoxanthophyll is a biomarker pigment of filamentous cyanobacteria, so the hypothesis was rejected. Our results also suggest that rotifers converted β-carotene provided by ingested algae into echinenone, a photoprotective pigment. This study, which is the first one to detail in situ pigment contents of rotifers, clearly shows that the role of cyanobacteria as a food source for meiobenthic invertebrates has been underestimated so far, and deserves urgent consideration.

Autor: Benoit Mialet , Nabil Majdi, Micky Tackx, Frédéric Azémar, Evelyne Buffan-Dubau



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