CYTOPLASMIC MICROTUBULES

TLDR

Small cytoplasmic tubules (~180 Å outer, 80 Å inner diameter, ~50 Å wall) are found in Hydra interstitial cells and cnidoblasts, occurring in intercellular bridges, free in cytoplasm, and associated with centrioles and nematocyst frameworks. Here, these tubules are termed microtubules and are proposed to mediate transport of water, ions, or small molecules. Microtubules are longer than 1.5 µ, cluster with Golgi vesicles in cnidoblasts, and form a tight skein with the cnidocil during late development.

Abstract

Small cytoplasmic tubules are present in the interstitial cells and cnidoblasts of hydra. They are referred to here as "microtubules." These tubular elements have an outside diameter of 180 A and an inside diameter of 80 A. By difference, the membranous wall is estimated to be 50 A thick. The maximum length of the microtubules cannot be determined from thin sections but is known to exceed 1.5 µ. In the interstitial cells the microtubules are found in the intercellular bridges, free in the cytoplasm and in association with the centrioles. In the cnidoblast they form a framework around the developing nematocyst and in late stages are related to the cnidocil forming a tight skein in the basal part of the cell. Especially in this cell, confluence of microtubules with small spherical vesicles of the Golgi complex has been observed. It is proposed that these tubules function in the transport of water, ions, or small molecules.