Gel electrophoreses of PCR products and the gray values from COI and 28S rRNA DNA amplification using the OSE (O) and GLB (G) extraction methods. (A) Electrophoretic map of the COI target fragment, lanes 1–3 were shell DNAs extracted by improved OSE, and lanes 4–6 were shell DNAs extracted by GLB; (B) electrophoretic map of the 28S rRNA target fragment, lanes 1–3 were shell DNAs extracted by improved OSE, and lanes 4–6 were shell DNA extracted by GLB; (C) gray values of the target fragment of COI; and (D) gray values of the target fragment of 28S rRNA. Each bar represents the mean ± SD (n = 3). ^** P < 0.01.