Figure 1.

Schematic representation of the life cycle of Schmidtea mediterranea asexual strain. Cycles of feeding and fasting are common during planarian life. During fasting the percentage of stem cells with long telomeres increases. Feeding induces a rapid proliferative response. During growing due to feeding, the stem cell pool decreases its telomere length. Red cells indicate stem cells with the longest telomeres while the orange show medium length and the green ones the shortest telomeres. Planarians are not to scale.