Symbiosis collapses during development of asexual offspring in the absence of heterotrophic feeding in a model cnidarian–algal symbiosis

A stable symbiosis between corals and dinoflagellate algae is crucial for coral reef health, and it is driven by nutrient exchange and environmental interactions. While homeostasis between cnidarian hosts and their algal symbionts during the adult stage has been well studied, far less is known about how this partnership is regulated during development and regeneration. We investigated the role of symbiotic algae and heterotrophic feeding on development in the sea anemone model organism commonly called Aiptasia. We focused on asexually-produced offspring (G1), examining the effects of autotrophic and heterotrophic nutrition on developmental rates. We found that the presence of symbionts enhanced growth in fed conditions but impeded development and survival under starvation. The effect of symbiont presence on starved offspring was dose-dependent, where those offspring with more symbionts at an earlier stage lost tentacles and mass faster than those with fewer symbionts. Our data demonstrate the importance of heterotrophic nutrition during early development and establishment of symbiosis. Our results provide insight into the metabolic costs and benefits of symbiosis under different nutritional conditions during development and regeneration of symbiotic cnidarians, and may have broader implications for understanding symbiotic stability and dysbiosis across diverse cnidarian–algal partnerships, including those in reef-building corals.