Curculionichthys tukana is distinguished from its all congeners, with the exception of C. karipuna and C. oliveirai, by having one abdominal median plate series (vs. three or more abdominal medial plates series); from C. karipuna by the lack of an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portion of the first unbranched anal-fin ray (vs. such pigmentation pattern present); from C. oliveirai, and also from C. insperatus, C. paresi and C. sagarana, by having seven to eight plates in abdominal lateral plates series (vs. four to six plates in abdominal lateral plates series); from C. itaim, C. luteofrenatus and C. piracanjuba by having papillae aligned in series that extends from the distal portion of lower lip to dentary (vs. all papillae randomly distributed throughout lower lip). Furthermore, Curculionichthys tukana can be separated from C. insperatus and C. oliveirai by lacking large conspicuous odontodes forming rows on head and trunk (vs. large, conspicuous odontodes forming rows on the head present); from C. oliveirai and C. coxipone by having the anterior profile of the head pointed (vs. anterior profile of head rounded); from C. paresi by having 12-18 premaxillary teeth (vs. 6-10) and 10-16 dentary teeth (vs. 4-7); from C. sabaji by the absence of dark-brown spots scattered over the body (vs. the presence of dark-brown spots); from C. paresi by absence of contrasting dark spots at the anterodorsal region of body (vs. the presence of such pigmentation pattern). In addition, Curculionichthys tukana can be differentiated from C. piracanjuba by having odontodes forming aligned rows, more evident in the dorsal portion of head and in the lateral portion of caudal peduncle (vs. odontodes not forming rows on the supraoccipital, on the compound pterotic, and on the lateral plates series) (Ref. 118146).

Description: Dorsal-fin rays ii,7; anal-fin rays i,5; pectoral-fin rays i,6; pelvic-fin rays i,5 (Ref. 118146).