Leucos ylikiensis is distinguished by the following characters: moderate size, not exceeding 12-13 cm SL; lack of a mid-lateral band; peritoneal membrane blackened by dense melanophores; lateral line usually with 42-43 pored scales. It differs from Leucos aula by its lack of lateral band and by having black peritoneal membrane (vs. silvery). It can be diagnosed from all others congeners by having usually 18-20 total gill rakers (vs. 8-16). It is most closely related to L. panosi from western Greece due to geographical position and based on molecular analyses. Four specimens from Lake Volvi with 17-18 total gill rakers and 41-42 scales on lateral line are identified as L. ylikiensis introduced in this lake (Ref. 96829).