Danio annulosus Lake system in Rangamati district in the Chittagong division, Bangladesh. The species name annulosus is derved from the neo-Latin word meaning "ringed", from the color pattern on the side of the fish which resembles a pattern of dark rings. "Danio annulosus" is so far known only from a small pool below the Shuvolong waterfalls during the summer when the water was stand still in the pool. There is a good chance of finding them in Kaptai lake system formed by the damming of Karnafuli River, as a small stream drains the pool to kapati lake. "Danio annulosus" is the 25th
Danio margaritatus with a markedly blunt snout, measuring just 2–2.5 cm standard length. The body is about three times as long as it is high. In general shape, it resembles "Danio erythromicron" more than any other known species. This species shows some sexual dimorphism: males have a bright-blue background color (dull blue-green in females), and their fins are more brightly colored. The tail end of their bodies (the caudal peduncle) is also higher than in females. The body is sprinkled with small, pearly dots. The back is bronzy green, and the belly in females is yellowish-white. The gill covers are transparent, letting