Investigating the alimentary tract in several species of lizardfishes (Synodontidae, Teleostei) of the genera Saurida, Synodus and Trachinocephalus, from various sites of their distribution, revealed melanization of the tract wall. This phenomenon was observed in several species of the genus Saurida, but not in the other two genera. This melanization is caused by layers of melanosomes rich in melanin granules and deposited within the connective tissue of the submucosa, between the muscular wall and the muscularis submucosa. From this site this black submucosa extends into the folds of the mucosa. In S. tumbil and S. filamentosa, the entire alimentary tract is black, whereas in S. macrolepis only the stomach is partially or entirely black. This phenomenon and its possible importance are discussed.
Fishelson, L., Golani, D., Russell, B., Galil, B., & Goren, M. (2012). Melanization of the alimentary tract in lizardfishes (Teleostei, Aulopiformes, Synodontidae). Environmental Biology of Fishes, 95(2), 195-200. https://doi.org/10.1007/s10641-012-9982-8