Immunohistochemical localization of vitellogenin in the hepatic diverticulum of the amphioxus Branchiostoma belcheri tsingtauense, with implications for the origin of the liver

Abstract. The localization of vitellogenin (Vg) remains untested in amphioxus. Western blotting analysis showed that mouse anti-amphioxus Vg sera cross-reacted with the crude extracts of the hepatic diverticulum and ovary, and humoral fluids, including blood and coelomic fluid, from specimens of Branchiostoma belcheri . Similarly, immunohistochemical staining also revealed that Vg is localized in the hepatic diverticulum, sub-intestinal vessels, and ovary in amphioxus. The hepatic diverticulum of amphioxus, like the vertebrate liver, synthesizes Vg, suggesting that amphioxus hepatic diverticulum is functionally equivalent to the vertebrate liver in respect of the synthesis of this compound. This agrees with the idea that amphioxus hepatic diverticulum is the precursor of vertebrate liver.