It's probably a butterfly. Considering Bulbapedia says so and the official page mentions its use of scales to heal others, that would make sense. Plus, sticking out of its back is a '3' shape that probably represents the wings of a butterfly. When it's closed up it might look something like this:
The black being the actual body itself and the red is me adding other features to make you see the resemblance (which was probably completely unnecessary but you know it's on the internet forever now so).
Furthermore, Bulbapedia says that 'lele' originates from the word 'pulelehua', Hawaiian for butterfly.
So yeah, probs a butterfly. I'm waiting to get proven wrong though.
Hope I helped. :)
Source: Above comment (lol thnx) and Leonardo da Vinci.