Rodlet cells in the alimentary tract of three genera of lizardfishes (Synodontidae, Aulopiformes): More on these enigmatic "gate-guards" of fishes

Rodlet cells (RCs) of the alimentary tract were studied in lizardfishes (Synodontidae) of the three major genera: Synodus, Trachinocephalus and Saurida, collected from the Mediterranean, the Red Sea, the South-African coast and the Great Barrier Reef (GBR), Australia. In the studied species two forms of RCs were revealed: one elongated, resembling those previously described from other fishes; and a second, bulbous in form, which was discovered in two species only, Saurida filamentosa and S. argentea from the GBR. In all species studied the cells are situated in the mucosal epithelium: the elongated form close to the luminal surface of the epithelium, and the bulbous form deep among the other cells. The two forms also differ in their microstructure, and their different positions in the epithelium activate different paths for release of the rodlets into the lumen. Each cell contains 15-30 rodlets, which change from round to needle-shaped during maturation, and are later released into the gut lumen. The development of the rodlets and the possible role of the RCs are discussed.