Contrasting Larval Phenotypes in the Reef-Building Coral Stylophora pistillata Suggest a Diversified Bet-Hedging Strategy

Environmental variability may favor offspring with contrasting phenotypes, yet its role in coral persistence is poorly understood. We compared planulae at the high- and low-fluorescence extremes of the phenotypic range in Stylophora pistillata. High-fluorescence and non-fluorescent planulae harbored similar Symbiodiniaceae communities but differed in morphology, physiology, tissue organization, and gene expression. HF planulae were larger, exhibited elevated green fluorescent protein intensity, and had lower baseline respiration. NF planulae had a thicker ectoderm and a higher putative lipid-utilization index. HF larvae showed higher GFP-like and biomineralization-associated gene expression, whereas NF larvae were associated with environmental sensing and cellular stress regulation. Across separate temperature, pH, and light experiments, HF larvae settled at a higher proportion than NF larvae in six of the seven conditions, although no individual treatment comparison was significant; phenotype affected settlement only within the pH experiment in axis-specific models. Post-settlement respiration showed a phenotype-by-condition interaction only in the pH experiment, and Photosystem II functional absorption cross-section was higher in HF-derived polyps across all three axes, whereas Fv/Fm and symbiont density did not differ. These findings identify intracolonial larval variation associated primarily with host traits, some persisting through early settlement, and suggest a basis for diversified bet-hedging.