Diagnosis: A species of Bedotia that uniquely possesses a distinctive crescent-shaped to semi-circular spangle on the posterior half of many opercular and flank scales, forming golden, occasionally whitish to bluish, iridescent highlights (Ref. 84245). Bedotia alveyi is further distinguished from congeners by a single diffuse broad midlateral band, vs. two distinct bands in B. geayi and B. madagascariensis, and absence of bands in B. masoala and B. marojejy; sparse and irregular lateral blotching between scales when alive, vs. extensive spots and/or blotches present in life and preservation in B. leucopteron, B. marojejy, and B. masoala; the absence of broad white margins on the second dorsal and anal fins, vs. white margins in B. albomarginata; and rust-red caudal-fin lobes, vs. hyaline to orange in B. longianalis and broadly outlined in black in B. tricolor (Ref. 84245).

Description: Average-sized bedotiid, reaching approximately 90 mm standardlength; shallow bodies and laterally compressed, standard length on average 4.5 times greatest body depth (Ref. 84245). Mouth oblique and moderately to strongly prognathous; posterior tip of maxilla reaches vertical midway between anterior orbital margin and pupil; snout acute in lateral profile, depressed and concave between premaxilla and orbit; eye moderate in size, orbit diameter approximately equal to one-fourth to one-third of head length; premaxillary 'Bedotia notch' pronounced (Ref. 84245). First dorsal fin inserted slightly posterior to vertical through anal-fin origin; second dorsal fin inserted posterior to vertical through anal-fin origin, a distance approximately equal to one-third of anal-fin base; first dorsal fin with 5-7 weak unbranched rays; second dorsal fin with 11-18 rays; anal fin with 17-22 rays; first two to four rays of second dorsal fin unbranched; anal fin with three to five unbranched rays; caudal fin emarginate to moderately forked; posterior margin of second dorsal and anal fins pointed and elongated in males, rounded in females (Ref. 84245). Scales large, imbricate, and cycloid, reduced in size on breast and caudal-fin base; hypural flexure followed by three or four rows of small cycloid scales extending onto base of caudal fin; head asquamate from snout to posterior of orbit, with the exception of large embedded pre-dorsal scales along dorsal midline, which may reach midorbit; cheek and operculum scaled; lachrymal, interopercle, and subopercle asquamate; predorsal scales number 16-18; scales in lateral series 36-39 (Ref. 84245). Interior and exterior surfaces of premaxilla, maxilla and dentary covered with small, slightly recurved, cylindrical teeth, with largest teeth located on dorsal surface of dentary opposite 'Bedotia notch' of premaxilla; three or four rows of similar teeth on vomer, arrayed in narrow crescentic patch extending to palatine; palatine teeth present; tooth patch present on endopterygoid, extending to quadrate; small ectopterygoid tooth patch present; tooth patches present on basibranchials one and three (Ref. 84245). Three or four short, stout hypobranchial rakers on first gill arch, becoming more elongate posteriorly; seven to nine slender, triangular ceratobranchial rakers, including raker in angle of arch; three or four short epibranchial rakers with bases approximately equal to length; all rakers, except epibranchial, denticulate for length of mesial surface; epibranchial rakers denticulate apically (Ref. 84245). Total vertebrae modally 36, comprising the following precaudal and caudal elements, respectively: 20+16, 19+17, 20+17, 20+15, 21+16, 19+16; posterior six or seven caudal vertebrae show typical marked thickening and crenulation characteristic of bedotiids (Ref. 84245).

Colouration: Colouration in life: base colouration yellowish-tan to olive dorsally, becoming lighter ventrally; broad diffuse midlateral stripe irregularly interrupted by iridescent, golden spangling on scales, resulting in a somewhat blotchy appearance midlaterally; opercle also with iridescent golden spangling on scales; iridescent golden colouration may extend above lateral stripe; thin silver or golden reflective line apparent in most specimens from pectoral-fin insertion to caudal flexure, merging with dark midlateral stripe below second dorsal-fin insertion to caudal fin base; pupil surrounded by bright golden ring; breast ventral to midlateral stripe variably iridescent golden or silvery; pectoral-fin base dark black; caudal-fin lobes rust-red; triangular spot at caudal flexure; procurrent caudal-fin rays pigmented, forming opposing spots dorsally and ventrally at caudal-fin base; central rays of caudal fin iridescent golden; anal fin with wide submarginal band anteriorly, becoming yellow or rust-red posteriorly; anal fin with black marginal band; black stripe present along anal-fin base (Ref. 84245). Colouration in alcohol: base colouration light tan to cream, becomong darker dorsally; dark, but diffuse, black midlateral stripe approximately on scale in height extends from snout to caudal-fin base; midlateral stripe interrupted across preopercle at level of orbit; in larger specimens, midlateral sripe becoming gradually less distinct anteriorly; melanophores on flanks concentrated at scale margins, producing reticulate pattern; reticulate pattern less distinct below lateral stripe; thin line of melanophores visible beneath squamation, following division between hypaxial and epaxial musculature, forming narrow stripe beginning six to eight scales posterior to angle of opercle and extending to hypural flexure; this line bifurcating into two subparallel lines beneath midpoint of second dorsal fin; caudally directed triangular patch at hypural flexure; upper and lower caudal rays pigmented at base, creating two distinct dark blotches, with pigmentation extending to both dorsal and ventral procurrent caudal rays; central rays of caudal fin pigmented and forming distinct stripe; stripe darkest at fin base; caudal-fin lobes hyaline distally; first dorsal fin with white to hyaline interradial membranes; white pigmentation patchy on distal half of fin; first dorsal rays pigmented except tips of first and second rays, which are white or hyaline; second dorsal fin with melanophores on membranes and ray margins, forming central stripe between translucent basal and marginal zones; central zone of pigmentation on second dorsal with narrow projections 'radiate' outward to fin margin, creating serrated appearance; margin of membrane between penultimate and last ray with dense black pigment; ray tips generally hyaline; anal fin with four bands of pigment from base to distal margin, comprising distinct narrow dark basal stripe, followed by lighter pigmented band, clear band, and elongate black marginal splotches on interradial margins, in most cases confined to anterior half of fin; membrane between penultimate and last ray generally with similar black pigmentation at margin; each pectoral-fin ray outlined with two rows of minute melanophores; axil of pectoral fin liberally blotched with black pigment; pelvic fins hyaline (Ref. 84245).