A Vital Staining Practice That Discerns Ancestry within Groups of Settling Larvae of a Brooding Coral

Xenogeneic and allogeneic encounters following aggregated and clustered settlements of coral larvae (planulae) may carry important ecological consequences in shaping coral reefs’ communities. However, larval settlement behaviors and settlement location choices in the presence of conspecifics or heterospecifics have not been examined in detail, due to a lack of experimental tools. One potential approach is the employment of vital staining of planulae with dyes that do not impair larval metamorphosis processes, are stable for prolonged periods, and do not diffuse to un-labeled counterpart planulae. For these purposes, we examined the use of neutral red (NR) dye, as an identification marker, on the planulae of Stylophora pistillata, a Red Sea branching coral species. To examine possible NR impacts on larval settlement in the presence of conspecific planulae, we followed the settlement ratios of kin, non-kin, and mixed assemblages, as a proxy for metamorphosis success. We found no differences in settlement rates of stained vs. unstained larvae, lack of stain diffusion to other larvae and that NR stain is maintained for more than a week under a still water regimen. Thus, staining with NR may serve as a useful experimental tool, opening new opportunities in studying larval settlement patterns in sessile marine organisms.