When first described, Danionella translucida was the smallest ostariophysan and the smallest adult vertebrate to inhabit fresh water.[3] Its adult size ranges from 10–12 millimetres (.43–.47 in) SL.[3]D. mirifica gets slightly larger, at about 14 mm (.55 in) SL, but is still one of the smallest freshwater fishes.[1][4]
D. mirifica has a single row of melanophores between the pelvic fins and the tips of the cleithra, and there is a lack of melanophores on the underside of the abdomen.[1]
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.[6]
^ abcRoberts, Tyson R. (1986). "Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest living vertebrates". Environmental Biology of Fishes. 16 (4): 231–241. doi:10.1007/BF00842977.