Cassiopeia is a marine organism with a medusa body that has an unusual orientation: it floats upside-down. it also has a distinct coloration that is due to algae that live between the epidermis (outer) layer and gastrodermis (inner layer that lines the digestive cavity) of the cassiopeia. the algae provide food for the cassiopeia, and the cassiopeia's orientation provides sunlight to the algae for photosynthesis. cassiopeia is a/an and the cassiopeia and the algae have a relationship.