Marine animals like jellyfish, corals and sea anemones often live with algae inside their cells in a symbiotic relationship. The animals give the algae nutrients and a place to live; in return, algae give the animals some of the food they make from sunlight via photosynthesis.

While this food production seems great for the jellyfish, the algae can also change its host animal’s immunity, similar to the changes made by human pathogens, like parasites that cause malaria. This side effect of the partnership weakens the jellyfish’s immune system, making them worse at fighting off infections.

Source :

Trade-off between photosymbiosis and innate immunity influences cnidarian’s response to pathogenic bacteria

https://royalsocietypublishing.org/doi/10.1098/rspb.2024.0428#d1e1971