Phyllodesmium longicirrum is probably the most spectacular of the aeolids which have evolved a symbiotic relationship with single-celled plants (zooxanthellae). It is exceptionally large, the shot with the two nudis, both are probably over 15cms long, and the cerata have evolved into large flattened “solar paddles” to maximise the animal’s ability to “farm’ the plants in its body.
The two nudis are feeding on the soft-coral Sarcophyton, where it probably gets the zooxanthellae from. It obviously has a symbiotic relationship with zooxanthellae, and these zooanthellae which is stores in it’s lobes, provide energy via photosynthesis. A remarkable creature.