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Danionella translucida


Danionella translucida
Micro Glass Danio
超迷你斑马
All species of Danionella are found in Myanmar. D. translucida is described from the Ayeyarwady River basin, and D. mirifica was described from the Kaiming area in upper Myanmar.
When first described, Danionella translucida was the smallest ostariophysan and the smallest adult vertebrate to inhabit fresh water. Its adult size ranges from 10–12 millimetres. D. mirifica gets slightly larger, at about 14 mm (.55 in) SL, but is still one of the smallest freshwater fishes.
Danionella species lack scales, barbels, and lateral line.
Observed in life, D. translucida is almost perfectly transparent except for its eyes. It has a distinctive pattern of melanophores. There are no melanophores on the dorsal surface except on the head over the posterior part of the brain. On the posterior half of the body, there a few melanophores following the horizontal midline. The sides and underside of the abdomen have melanophores. A double row of melanophores is present on the underside of the fish from the isthmus of the gills to the pelvic fins. D. mirifica can be differentiated with its melanophores; in D. mirifica, there is only 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.
Eggs in D. translucida has been found to range in size from about .3–.6 mm in diameter, with ripe eggs being at least .5 mm in diameter. Females carried anywhere from 3 to 8 or 10 eggs. Compared to the body of the fish, these eggs are relatively large.
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 the use for sparring for mates. Britz et al. believe the lineage lost true teeth about 50 Ma.
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