The fine structure of the gastric caeca of Aedes aegypti larvae

Abstract

The gastric caeca of Aedes aegypti possess inner longitudinal and outer circular striated muscles. The caeca are subtended by a generally thick, spongy basement lamina composed of irregular layers of particles. The basal portion of a caecal cell contains numerous, intracellular, clear, highly irregular, sac-like expansions which are elaborately interconnected. They open onto the basement lamina. Numerous large mitochondria with dense cristae are packed in the cytoplasmic matrix between the clear, labyrinthine, sac-like expansions. The apical portion of a caecal cell possesses numerous, long, thin microvilli which contain fine, parallel rows of microfilaments which extend to the very tip of each microvillus. The microvilli lack glycogen and have no mitochondria. The apical half of the cells contains many, large mitochondria, microfilaments, and tubules. No centrosomes were found. Nerves were not seen on or near the caecal cells. Since the caecal cells examined apparently lack a recognizable Golgi zone, a highly organized, rough-surfaced endoplasmic reticulum, lysosomes, and secretory granules, they cannot be considered secretory. The fine structure of the caecal cells indicates that they are concerned mainly with absorption of fluids, and this is in agreement with the physiological observations of earlier workers.