biostudies-literatureChan WYNational Health and Medical Research CouncilWestpac Research FellowshipAustralian Research Councile70011https://www.ebi.ac.uk/biostudies/studies/S-EPMC11751664biostudies-literatureUnknown27(1)Symbiotic cnidarians, such as sea anemones and corals, rely on their mutualistic microalgal partners (Symbiodiniaceae) for survival. Marine heatwaves can disrupt this partnership, and it has been proposed that introducing experimentally evolved, heat-tolerant algal symbionts could enhance host thermotolerance. To test this hypothesis, the sea anemone Exaiptasia diaphana (a coral model) was inoculated with either the heterologous wild type or heat-evolved algal symbiont, Cladocopium proliferum, and homologous wild-type Breviolum minutum. The novel symbioses persisted for 1.5 years and determined holobiont thermotolerance during a simulated summer heatwave. Anemones hosting SS8, one of the six heat-evolved strains tested, exhibited the highest thermotolerance. Notably, anemones hosting the wEnvironmental microbiologyHeat-Evolved Microalgae (Symbiodiniaceae) Are Stable Symbionts and Influence Thermal Tolerance of the Sea Anemone Exaiptasia diaphana.PMC11751664FL180100036APP1154540DE240100317Chan WYDoering TNarayana VKSakamoto RDe Souza DPMcConville MJvan Oppen MJHfalseHeat-Evolved Microalgae (Symbiodiniaceae) Are Stable Symbionts and Influence Thermal Tolerance of the Sea Anemone Exaiptasia diaphana.Symbiotic cnidarians, such as sea anemones and corals, rely on their mutualistic microalgal partners (Symbiodiniaceae) for survival. Marine heatwaves can disrupt this partnership, and it has been proposed that introducing experimentally evolved, heat-tolerant algal symbionts could enhance host thermotolerance. To test this hypothesis, the sea anemone Exaiptasia diaphana (a coral model) was inoculated with either the heterologous wild type or heat-evolved algal symbiont, Cladocopium proliferum, and homologous wild-type Breviolum minutum. The novel symbioses persisted for 1.5 years and determined holobiont thermotolerance during a simulated summer heatwave. Anemones hosting SS8, one of the six heat-evolved strains tested, exhibited the highest thermotolerance. Notably, anemones hosting the w2025-01-01T00:00:00Z2025 Jan2026-05-29T17:03:20.324Z2025-04-05T11:34:20.324ZS-EPMC117516643983880310.1111/1462-2920.70011