Glass Danio "Cerebrum" Danionella cerebrum

Danionella cerebrum is one of several micro glassfish in its genus. It is one of the smallest freshwater fish in the world, growing to 10-13mm long, together with D. translucida, the Jorai Glassfish and Dracula "Minnow". A schooling fish, it is endemic to low altitude, small, slow-moving streams, creeks and canals in Myanmar and looks like a transparent larval fry.

Its properties have made it particularly useful to science: despite having the smallest brain of any fish, the workings of the active brain can be observed through the transparent skin. Moreover, males produce a noise with their swim bladder to alert mates/rivals in the murky water that is the loudest noise for its size (louder than an elephant relative to size), said to be like a gunshot or 140 decibels close to the fish.