The distribution and function of microtubules in nutritive tubes

The density and distribution of microtubules in the nutritive tubes of three hemipteran insects, Corixa punctata, Notonecta glauca and Dysdercus cingulatus, were analysed from electron micrographs by computer. Both parameters varied amongst all three species, the density of microtubules in Corixa being approximately three times that seen in Dysdercus. The density and distribution of microtubules within the nutritive tubes correlated directly with the size of particle transported by them, suggesting that the microtubules may act as a sieve to preclude certain cellular components from entering the tubes. If microtubules are further involved in the generation of motive force for cytoplasmic transport along the nutritive tubes, this function is not dependent upon the number of microtubules, or upon their arrangement with respect either to each other or to the particle being transported.