Even if benthic sessile organisms, such as corals and anemones, are known to attract fishes and invertebrates in benthic tropical ecosystems, our knowledge of chemical mediations in benthic ecosystems is still very limited especially in temperate areas. So far, most studies have indeed been restricted to defensive strategies between benthic organisms. Sponges are sessile filter feeders dominant in several ecosystems. They are also known to produce a large chemical diversity. We therefore hypothesized that sponges release chemical cues in their surrounding seawater which might influence the behavior of various mobile organisms and would contribute to benthic ecosystems structuring and functioning. We decided to focus our attention on submarine cave ecosystems because they harbor much stable environmental conditions and sessile species assemblages that are dominated by sponges.

Using two- and four-choice tests systems, we observed the response of two cave-dwelling crustaceans (Hemimysis margalefi and Palaemon serratus) and two other species which are living in shallow water environments (Leptomysis sp. and P. elegans) to the surrounding seawater of four Mediterranean sponge representatives of marine cave entrances: Aplysina cavernicola, Haliclona fulva, Oscarella tuberculata and Spongia officinalis. Both cave-dwelling species, H. margalefi and P. serratus, were significantly attracted by sponge chemical cues, while Leptomysis sp. spent more time in the reference seawater and P. elegans had indifferent responses. Four-choice tests revealed that both cave-dwelling species responded differently to the four sponge species taken individually. To our knowledge, this is the first evidence of the attractive potential of sponge chemical cues to the mobile fauna.