Melatonin, the molecule signaling darkness, is possibly related with the development of the vertebrates. In developing chick retinas, Mel1a-like melatonin receptor (Mel1a) has been observed at embryonic day (E) 8 and after. NRH: Quinone reductase enzyme (QR2) is a detoxifying enzyme that binds melatonin analogs in developing chick retinas. In this study, whole mounted E21 embryos and whole retinas of the E21 embryos and juvenile Kinosternon scorpioides (JKs) were submitted to immunoassays to investigate the presence of Mel1a and QR2. Texas Red immunofluorescence for QR2 and Mel1a was diffusely localized in whole retinas of the E21 embryos and of the JKs. In E21 whole embryos, Texas Red immunofluorescence for Mel1a was localized in forelimb, hindlimb, peripheral carapace and tail. Mel1a immune signals were also present in choroid fissure of the optic cup, and in a region that corresponds to frontonasal process, mandibular process and maxillary process. QR2 was present in maxillary process region, in lens/iris, forelimb, hindlimb and tail. The results suggest that melatonin must have functions in testudine development by binding Mel1a and QR2.
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