Juvenile Acropora tenuis attract Symbiodinium by using GlcNAc-binding lectin

Most reef-building corals acquire symbiotic dinoflagellates, Symbiodinium spp., from surrounding environments and establish symbiosis with Symbiodinium [1-3]. Although, Symbiodinium are present at low densities under natural environmental conditions, corals acquire Symbiodinium effectively [4]. This therefore raises the possibility that corals acquire Symbiodinium by utilizing chemotactic compounds. Recently, Yamashita et al. reported that juvenile Acropora tenuis, appears to attract Symbiodinium during the initial stage of symbiosis [5]. Furthermore, it has been reported that N-acetyl-D-glucosamine (GlcNAc) binding lectin in A. tenuis, ActL, attract Symbiodinium NBRC102920 strain which is acquired by juvenile A. tenuis polyps [6]. Interestingly, Kuniya et al. showed that juvenile A. tenuis polyps acquire only few Symbiodinium strains among tested [7], suggesting that A. tenuis contains chemotactic compounds that can attract specific Symbiodinium strain. In the present study, we examined the chemotactic activity of ActL to six Symbiodinium culture strains and examined whether juvenile A. tenuis polyps discharge ActL to consider ActL could be a factor of symbionts selection.