| Abstract: | The ultrastructure of lymphatic capillaries in the tail fin of Rana catesbiana larvae was investigated. With the use of a colloidal marker particle (Biological Carbon) the extent that these delicate vessels ramify throughout the fin region was demonstrated. This opaque substance also serves as a marker particle for identification of lymphatics with some degree of certainty at both light and electron microscopic levels. The cytoplasm of the lymphatic endothelial cell is abruptly attenuated beyond the perinuclear region, reaching widths as thin as 300 Å. Lymphatic Anchoring filaments are present, but to a lesser degree than noted for other species studied. Other features of interest include an extensive Golgi complex and electron dense bodies that are surrounded by a smooth surfaced unit membrane. These bodies are somewhat heterogeneous in size (500 Å up to 0.5 μ in diameter) and density. Numerous exit channels are provided by the extensive supply of lymphatics throughout the tail fin region of amphibian larva thus allowing them to serve an important function during metamorphosis. It is suggested that these vessels also act as passageways through which lysed cellular and connective tissue components may be rapidly removed during the process of tail fin resorption. |
