Corydoras apiakacan be diagnosed from its spotted congeners by having smaller dorsal-fin spine than the three anterior branched dorsal-fin rays (vs. dorsal-fin spine smaller than just two anterior dorsal-fin rays, or equal in size). It differs from its congeners, with the exception of C. albolineatus, C. araguaiaensis, C. haraldschultzi, C. julii,C. polystictus, C. multimaculatus and C. xinguensis, by having numerous dark-brown spots over the head and body (vs. absence of spots). It can be distinguished from C. albolineatus, C. araguaiaensis and C. haraldschultzi by having several spots scattered all over the head and trunk in a somewhat random pattern (vs. spots more concentrated and with a single pale horizontal stripe in the middle of the body in C. albolineatus; or spots arranged in three or more stripes along the trunk in C. araguaiaensis and C. haraldschultzi); pectoral, pelvic and anal fins hyaline (vs. several series of small blotches over fin rays), and adipose fin hyaline or bearing one spot (vs. two or more spots). Corydoras apiaka further differs from C. multimaculatus and C. xinguensisby the absence of blotches on interradial membrane of dorsal fin (vs. presence); adipose fin hyaline or with a single spot (vs. two or three well defined spots); spots not reaching over the anal fin base (vs. spots extending to anal-fin base). It is distinguished from C. xinguensisby the absence of spots onanal fin (vs. presence); body spots with diffuse border (vs. spots with well delimited edge). It can be further separated from all other spotted species, except C. multimaculatus, by the naked ventral region (vs. belly with small platelets) (Ref. 102660).

Description: Anal-fin rays ii,5,i; pelvic-fin rays i,5 (Ref. 102660).