On the ultrastructure of the ventricular endocardium and bulbar endothelium in 3 teleostean species.

The endocardium in the ventricle and the endothelium in the bulbus arteriosus are described in 3 phylogenetically distant teleostean species, Betta splendens, Pistella riddlei, and Xiphophorus maculatus. The ventricular endocardial cells are attenuated and contain a number of bristle-coated vesicles (BCV). In the former 2 species these cells contain numerous ribosomes, a low number of moderately electron dense bodies (MDB) and a poorly developed agranular endoplasmic reticulum (AER). In the latter species, however, these cells are poor in ribosomes, but very rich in MDB and AER. In the species studied the bulbar endothelial cells contain high numbers of ribosomes, whereas BCV and AER are poorla developed. In P. riddlei these cells have a height of 3-7 microns and are closely packed by MBD, whereas in B. splendens and X. maculatus they appear to be flat and contain a very low number of MDB. The results of the present work are compared with those scare findings previously reported for the teleostean ventricular endocardium. The structural differences described may reflect phylogenetical distances.