Figure 6. Gene expression patterns of putative melatonin receptors in Nematostella vectensis.

Two representative melatonin receptor orthologs were evaluated using in situ hybridization (ISH) with specific probes. (A, B) A similar expression pattern between orthologs in adult polyps was observed and indicated that the mRNA for the putative receptor was predominantly expressed in the circumference of the actinopharynx (ph) and at substantially lower levels in the hypostome. (C) Higher magnification of the actinopharynx area indicated that the melatonin receptors are also expressed in the inner epithelium (arrowhead); albeit at lower levels (D) Substantial melatonin receptor expression was evident in fertile gonads (peripheral surfaces of endodermal cells), implying a reproduction-related receptor-mediated mechanism of action for melatonin. (E, F) The expression of putative melatonin receptors in the body wall was predominantly characterized by an endodermal distribution but was also sporadically observed at lower levels in both ectodermal cells and in the epithelial muscular layer (arrowheads) at the base of the endoderm. Scale bars: A = 500 µm; B = 200 µm; C = 100 µm; D, E = 50 µm; F = 20 µm.