Can you tell the age of a starfish by the number of arms it has?

No, the number of arms on a starfish does not necessarily correspond to its age. While starfish typically have five arms, some species can have more or fewer arms, and the number of arms can also change over time due to regeneration or other factors. Age determination in starfish is generally done by examining their growth rings or ossicles, which are small calcified structures in their arms that can be used to estimate their age. The growth rings can be counted similarly to tree rings, but the accuracy of the method can vary depending on the species, environment, and other factors.

It's also worth noting that starfish, also known as sea stars, don't have a specific lifespan like humans or other animals. Instead, they can continue to grow and reproduce throughout their lives as long as they don't succumb to disease, predation, or other threats.