Table 1. Criteria that support aging research in H. oligactis CS polyps undergoing sexual differentiation. For aging in humans, see (Lopez-Otin et al. 2013; Rai et al. 2014; and Sousounis et al. 2014).

Aging in humans	Aging in Hydra oligactis (CS strain)
Neurodegeneration	Disorganization of the apical nervous system and loss of neurons, loss of the feeding behavior (Yoshida et al. 2006; this work)
Loss of adult somatic stem cells	Dramatic reduction in the number of interstitial somatic stem cells (Littlefield et al. 1985; Yoshida et al. 2006)
Sarcopenia	Disorganization of the actin myofibers, loss of contractility, loss of food transfer to the gastric cavity (Yoshida et al. 2006)
100% mortality within 100 years after sexual maturity	100% mortality within 120 days after sexual differentiation (Brien 1953; Noda 1982; Yoshida et al. 2006)