This was one of many nudibranches we recently spotted on a stunning morning dive at Hin Dot, Phi Phi Don. The blue dragon (Pteraeolidia ianthina) is a sun-powered slug. It eats coral filled with tiny plants called algae. After eating the coral, the nudibranch keeps the algae in its cerata. There, the algae get to work. Algae, like other plants, use sunlight to make food through photosynthesis. Inside the slug's cerata, the algae keep using sunlight to make food. That food then fuels the nudibranch.
To keep their algae farms going, blue dragons must soak up a lot of sun. Hanging out in shallow water during the day helps them get the sun they need. After eating algae, the sea slug can go for days without another meal. It lives off the food being farmed inside its body - amazing!!
