Which of the following organisms is capable of reversing aging?

The correct choice highlights the remarkable regenerative capabilities of Hydra, a small, freshwater organism. Hydra has shown significant potential for reversing aging due to its unique biological properties. Unlike most multicellular organisms, Hydra exhibits negligible senescence, meaning it does not seem to undergo the typical aging processes that lead to a decline in reproductive capability and overall vitality. This quality allows Hydra to maintain a relatively constant population of stem cells, which can indefinitely regenerate its tissues.

Research indicates that Hydra’s ability to continuously renew its cells contributes to its longevity and lack of age-related decline. The organism’s biological mechanisms are under investigation to understand how they could inform human aging and regenerative medicine.

In contrast, while the other organisms mentioned possess interesting features regarding aging and longevity, they do not exhibit the same regenerative capabilities or arrest of aging. For instance, American lobsters are known for their longevity but age normally, and Bristlecone pines, while among the oldest living trees, also age in a traditional sense. Planaria are known for their impressive regenerative abilities, but they have not demonstrated the capacity to reverse aging in the way Hydra does.