Spontaneous loss of interstitial stem cells from hydra tissue

A spontaneous loss of interstitial stem cell population from normal hydra tissue was observed. A wild-type strain of Hydra magnipapillata was maintained in lines of individual polyps for many generations. In each line, the first generation was started from a single young polyp, and the first bud produced in one generation was used to start the next generation. Many lines maintained in this way (10/16) yielded polyps which exhibited limited feeding capacity, indicating reduced numbers of nematocytes and/or nerve cells in the tissue. Furthermore, a few lines (3/16) turned into "epithelial hydra" which could not move or feed and contained no interstitial stem cells or their differentiation products (nematocytes and nerve cells) in the tissue. Examination of the number and localization of interstitial cells in the tissue of various lines provided evidence which suggests that multiple factors, including reduced displacement of interstitial cells from parental to bud tissue, are responsible for the spontaneous loss of interstitial stem cell population observed.