Comparative scanning electron microscope studies of hepatic parenchymal architecture in the three infradivisions of teleosts

This report advances the phylogenetic hierarchy in teleosts with regard to micro?hepatic architecture. To demonstrate the correlation between liver structures and phylogenic status, we analyzed livers from nine teleost taxa using light and scanning electron microscope and subjected the data to phylogenic analysis. We observed that the hepatocytes were spread out as anastomotic cords, arranged in two to several cellular layers, and surrounded by sinusoids. We also found that in many species within the three infradivisions, hepatocyte nuclei were not centrally located, unlike the hepatocyte nuclei of mammals. The parenchymal arrangement evolved in parallel with phylogenic advancement. As phylogenic branching is graded in ascending order from the primary or secondary type to the final level, the parenchymal arrangements progressed from solid or tubular to cord?like, and the shape of hepatocytes changed from round to square and/or polyhedral. Thus, the hepatic lobular structures of the Euteleostei livers were more complete and of an advanced type, similar to that of mammalian livers. A phylogenic study of fish may be valid as an optimal model for liver ontogeny in vertebrates.