Ultrastructure and histochemistry of the ultimobranchial body of fresh-water turtles

The ultimobranchial body of fresh-water turtles,Pseudemys scripta andChrysemys picta, ultrastructurally and histochemically resembles the gland of other vertebrate groups and the homologous thyroid parafollicular cells of mammals. Characteristic features of all of these tissues are secretory granules measuring approximately 150–250 mμ, a distended endoplasmic reticulum, prominent Golgi regions and large numbers of free ribosomes. Unusual features of the turtle ultimobranchial body are an abundance of large cytoplasmic bodies measuring 800–1000 mμ and a dense, homogenous material within the lumina of the ultimobranchial follicles. The large cytoplasmic bodies usually occur near the luminal portion of the cells and are of similar electron density to the luminal contents, suggesting a possible functional relationship of these two glandular components.