Danio annulosus Kullander, Rahman, Norén & Mollah 2015

Danio annulosus can be diagnosed from other congeners, except D. assamila, D. dangila, D. catenatus, D. concatenatus, and D. sysphigmatus, by produced first ray in pectoral and pelvic fins, large cleithral spot, and pattern of dark rings enclosing light interspaces on the side. It differs from these species by slightly horizontally extended cleithral spot (vs. vertically extended in D. dangila, round in the other species), anterior interstripe Ia usually present (vs. absent in D. dangila and D. catenatus), rings in series along side elongate, width of each dark ring of about same as diameter of light centre or wider (vs. elongate, with narrower dark ring in D. sysphigmatus, round or slightly elongate and with dark ring about as wide as light centre in other species), ring pattern usually not extending onto caudal peduncle (vs. present on part of caudal peduncle in D. dangila, D. catenatus and D. concatenatus), 34- 35 lateral-line scales (vs. 35-38 in D. sysphigmatus), pectoral fin barely or not reaching to base of pelvic fin, unbranched leading ray only slightly longer than remaining rays (vs. leading ray prominently elongated, reaching to base of unbranched pelvic-fin ray or beyond), pelvic fin without produced unbranched ray, not reaching to vent (vs. with unbranched ray distinctly longer than the rest, and reaching to vent or bases of anterior anal-fin rays) (Ref. 104133).

Dorsal soft rays (total): 11 - 14; Analsoft rays: 16 - 18; Vertebrae: 36

Found at the foot of a waterfall draining into the Kaptai Lake, a reservoir formed by the damming of the Karnafuli River, completed in 1962. During the wet season, the fall has a height of about 100 m and falls directly into the lake. At the time of collection, the lake level was low: the waterfall had almost ceased and only some dripple moistened the rock. Water was retained in a small pool at the foot of the fall, at most about 40 cm deep, holding some pieces of rock but devoid of vegetation. Specimens were collected using seine from the deeper shadowed area of the pool along with numerous specimens of shrimp, snails, and a small species of Garra. The pool drained to the lake by a small stream, only about 1 cm deep. The following species were caught in the lake at the mouth of the stream using seine: Esomus danrica (Hamilton), Rasbora daniconius (Hamilton) (Cyprinidae), Dermogenys burmanica Mukerji (Zenarchopteridae), Aplocheilus panchax (Hamilton) (Aplocheilidae), and Trichogaster lalius (Hamilton) (Osphronemidae), which are considered ubiquitous species in Bangladeshi freshwaters (Ref. 104133).