Interstitial cells are located in clusters between muscle cells. It is called Reserve cell or Stem cell or multipotent cell. The cells appear round, oval or triangular in shape. Each cell contains a nucleus, numerous mitochondria, endoplasmic reticulum, lysosomes, ribosomes etc. It has totipotency capability. So it transforms into any other cell as needed. The diameter of the cells is 5 μm.
Function of interstitial cells
(i) A cell can transform into any other cell.
(ii) It participates in hydra regeneration, growth, gonad and bud formation.
(iiii) After 45 days, when body cells are destroyed, interstitial cells fill the space.