Fig. 1.

Inducible aging phenotype in cold-sensitive Hydra oligactis (Ho_CS). (A) Phylogenetic position of Hydra among metazoans. (B) Anatomy of a male H. oligactis animal. (C) Schematic view of Hydra gastric tissue. Mes, mesoglea. (D) Morphological changes observed in Ho_CS (top) and Ho_CR (bottom) animals at various time points after transfer to 10°C (day 0); arrowheads indicate testes, arrows indicate head regions. Scale bars: 500 µm. (E) Survival rates among Ho_CR and Ho_CS cohorts maintained at 10°C for 120 days. (F) Head regeneration in Ho_CR or Ho_CS animals selected for the presence or the absence of testes, bisected at mid-gastric level on day 24 post-transfer (dpt) and monitored for 24 days post-amputation (dpa). (G) Head regeneration measured in Ho_CS animals bisected at 18°C (blue, black) or at various time points after transfer to 10°C (9, 23, 30, 37 dpt) and monitored for 15 days.