Isolation of prolactin gene and its differential expression during metamorphosis involving eye migration of Japanese flounder Paralichthys olivaceus

•prl has the asymmetric distribution around the eyes during metamorphosis.•Colchicine inhibited prl expression in the suborbital area of the migrating eye.•MMI and 9cRA inhibited prl expression around the migrating eye.•PRL is involved in cell proliferation of migrating eye during flatfish metamorphosis.