The most bizarre existence of naked gill sea slugs.

Phylliroe, the most bizarre species of naked gill sea slugs, is a transparent sea slug that can swim freely in the sea. It completely abandons the stomach feet on which other gastropods move, and evolves a fish-like form with a false and true "tail fin". The swimming posture is similar to that of a real fish (Fig. 9), which is the most extreme example of convergent evolution. If there were not two identifiable antennae, it would be feared that Phylliroe would indeed be regarded as a primitive chordate such as amphioxus. Although seemingly delicate and harmless, Phylliroe, like most other naked gills, is a carnivore that preys mainly on jellyfish, and its fish-like form gives them the ability to search for prey efficiently.