科研之友
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摘要
Four Malpighian tubules of the leafhopper Kolla paulula (Walker) emerge from the junction of the midgut and hindgut, with terminal ends united in pairs and attached to half of the rectum. Each tubule has five structurally distinct regions: a thin anteriormost region, taking part in the formation of the filter chamber; a smooth and short intermediate duct; a long nodulose proximal segment; a glandular distal segment; and a long, thin and undulated terminal segment. The proximal region contains numerous hollow spherical nodules which are regularly arranged and form a spiral pattern. Its cytoplasm is packed with extensive rough endoplasmic reticulum and secretory granules. Clusters of fine electron-dense granules, glycogen granules and condensing vacuoles are prominent. This suggests that the proximal region is involved in secretion. Microorganisms are found in the cytoplasm and lumen of the proximal segment. The distal segment is rod-shaped, with cells filled with vacuoles containing hollow and honeycomb-surfaced microspheres known as "brochosomes", and four different stages of brochosome-development can be recognized. The terminal segment cells possess well-developed apical microvilli and basal infoldings associated with mitochondria. Rough endoplasmic reticulum, abundant mitochondria, and intracellular canaliculi densely packed with long microvilli are observed through the cytoplasm. These characters indicate the terminal segment is probably involved in secretion and ion transport.
