Our work provides strong support for the hypothesis that Sinularia flexibilis ingests diatoms such as Thalassiosira pseudonana. We assessed algal ingestion by S. flexibilis through estimates of algal removal, histological analyses, scanning electron microscopy observations, and gene expression determination (18S and silicon transporter 1) by real time PCR. Cell counts are strongly suggestive of algal removal by the coral; light and scanning microscopy provide qualitative evidence for the ingestion of T. pseudonana by S. flexibilis, while molecular markers did not prove to be sufficiently selective/specific to give clear results. We thus propose that previous instances of inability of corals to ingest algae are reconsidered using different technical approach, before concluding that coral herbivory is not a general feature.

Dipartimento di Biomedicina Comparata e Alimentazione Università degli Studi di Padova Agripolis Viale dell'Università 16 35020 Legnaro Italy

Dipartimento di Scienze della Vita e dell'Ambiente Università Politecnica delle Marche via Brecce Bianche 60131 Ancona Italy

Institute of Microbiology ASCR Centrum Algatech Laboratory of photosynthesis Opatovický mlýn 379 81 Třeboň Czech Republic

National Research Council Institute of Marine Science Venezia Italy

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