Localization of endobacteria in the gastrodermis of a Mediterranean gorgonian coral, Paramuricea clavata, using fluorescence in situ hybridization
Résumé
Gorgonian corals are among the most representative species of hard-bottom sublittoral ecosystems in the Mediterranean Sea. The red gorgonian, Paramuricea clavata, harbors a specific, spatially and temporally stable bacterial community that may have an important biological role in the function of the holobiont. However, little is known about the microbial–gorgonian relationship, specifically the nature of the interaction established by the bacteria with their host. Documenting the distribution of micro-organisms within coral tissue compartments is critical for providing an overall framework for understanding their
functional roles. Here, we used histology and fluorescence in situ hybridization (FISH) to detect and localize bacteria in the tissues of P. clavata. Aggregates of tightly packed bacteria were found in the endoderm of the polyps, which is consistent with previous observations of endobacteria in the tissues of scleractinian coral species. This finding suggests the existence of an intimate biological integration between specific members of the microbiota and gorgonian corals that likely results from a complex interplay mediating recognition and maintenance of the bacterial associates. In addition to providing the basis for the development of FISH studies in gorgonians, this work includes the first histological description of the inner structure of P. clavata polyps, illustrating the typical features of general gorgonian anatomy.