Fine Structure of the Cellular Parenchyma and Extracellular Matrix of <i>Ophiotaenia loennbergii</i> (Cestoda: Proteocephalidea)

Abstract

Abstract The cellular parenchyma and extracellular matrix (ECM) of Ophiotaenia loennbergii were studied by light and transmission electron microscopy. The parenchyma consists primarily of muscle cells divided into three compartments that maintain some cytoplasmic continuity: (1) myofibrils; (2) broadly lobate nucleated myocytons (muscle cell perikarya) with the perinuclear cytoplasm dominated by greatly dilated cisternae of granular endoplasmic reticulum: (3) thin anucleated sarcoplasmic extensions formed in sheets with abundant glycogen and extremely large lipid droplets, which cause the cytoplasmic sheets to bulge. These cellular compartments are separated from each other by abundant ECM, which consists primarily of an electron‐lucent amorphous ground substance. Filaments are scarce in all ECM except the tegumental basement lamella. This is the first report of parenchyma and ECM fine structure in the Proteocephalidea. The results provide additional evidence that cestode parenchyma is formed from similar cells, but is subject to substantial variability between different species.