Ultrastructure of the rotifer Brachionus plicatilis

The ultrastructural study of digestive organs andintegument of the rotifer, Brachionusplicatilis, was performed by transmission of electronmicroscopy to elucidate the relationship between theirstructure and function. The integument of the rotiferis composed of a thick external and a thin internallayer, in which many pores are regularly distributed.The contents of secretory bulb are excreted throughthose pores to the external surface. The inner surfaceof the digestive tract is lined with relatively denseand regularly spaced cilia for propelling food along.The cells of stomach and the intestine contains manyendocytotic vesicles, digestive vacuoles, and lipidinclusions, indicating its active endocytoticfunction. The gastric gland cells have abundant roughendoplasmic reticulum, Golgi complexes and secretorygranules for producing digestive enzymes. Thisultrastructural study clarifies the morphologicalcharacters of the integument and the digestive organsthat are closely related to its function.