Danionella

 ( Danioninae ) 

Danionella species lack scales and barbels, but possess a lateral line.

D. mirifica has a single row of melanophores between the pelvic fins and the tips of the cleithrum, and there is a lack of melanophores on the underside of the abdomen.

D. dracula reaches 17 mm in length. It is neotonous, lacking 44 bones that develop late in the related zebrafish Danio rerio. They have teeth made of bone, rather than the true teeth of other fishes, and the males have a pair of boney fangs which may be used during male-male competitions over nesting sites. Britz et al. believe the lineage lost true teeth about 50 Ma.Ralf Britz et al., Royal Society's journal Proceedings B, March 2009

A particular scientific advantage of an optically transparent organism is that it allows neural activity recordings (typically calcium imaging) to be performed in the same animal that will later be used for neural circuit reconstruction. This allows researchers to bypass many of the animal-to-animal variability problems caused when trying to correlate the behavior observed in one animal with the reconstructed circuitry of a different animal.