The ultrastructure of the saccus vasculosus of teleost fishes I. The coronet cell

Abstract

The ultrastucture of the coronet cell of a large number of teleosts belonging to different orders was investigated. Tubular and vesicular components of the smooth endoplasmic reticulum occur in coronet cells and in globules of all the species examined. Cell organelles such as lysosomes, Golgi systems, and mitochondria are predominantly located in the basal region of the cell. Modifications of the endoplasmic reticulum include whorls and vacuoles as well as honeycomb systems. In malacopterygian teleosts rootlets and filaments instead of microtubules occur frequently. The possibility of interconversion between these organelles is discussed. Acid phosphatase is found mainly in the lysosomes, but the granules contained in the stalked globules often contain acid mucopolysaccharide. It is suggested that new globules are formed by a process of pinching off of parts of the apical protrusion and the simultaneous growth of a modified cilium into it.