Unique croakers

Sundadanio are unlike other fish. In particular, the muscles and the bones of the males are significantly different to those of the females.

These differences serve a purpose. Though the exact mechanism isn’t known, males are able to generate a croaking sound, something they’ll regularly do when competing with rival males for dominance. The sound may also play a role in advertising their presence for breeding, and attracting mates in their gloomy, low-visibility habitats.