Does a Starfish Feel?

The starfish is a creature that has nerves, but no brain. It "feels" in the sense that it gets signals from nerves in its arms that cause it to move toward things positive, such as food, and away from things negative, such as being poked with a stick.

  1. Alive, Alive, O

    • The ability to feel, which scientists call responsiveness or irritability, is one of the eight functions that define a living thing. The starfish is made up of cells and it moves, digests, metabolizes, excretes, grows and reproduces. It has a functioning nervous system, albeit a primitive one, which fulfills the eighth requirement, so it's a living thing with the ability to feel.

    Master Plan

    • The starfish is organized on the scientific principle of radial symmetry: it has multiple identical appendages, called arms, that stick out from a central core, where its mouth is, but it moves according to neurological impulses received from the arms.

    The Arms Have It

    • Most starfish have five arms, but some have more. A nerve runs down each arm to control the many tube feet on that arm. This nerve provides both a sense of touch and a sense of taste. The starfish gropes its way along a coral reef or the sea floor by touch and follows chemical signals in the water that either attract or repel it. In the absence of a decision-making central brain, the arm that gets the strongest sensations leads the way.

    The Pain of It All

    • Whether any given living thing feels pain is the subject of much debate. The level of nervous system development seems to be the point of determination. A common expression is "No brain, no pain"̵2;in other words, in the absence of a highly developed nervous system with a central brain to coordinate a response, pain does not exist̵2;and science seems to confirm this. While it may be just local muscle reaction, though, it's hard for some to watch the brainless starfish writhe away from the stick. Until we can know for sure, it might be kinder to err on the safe side and avoid introducing noxious stimuli wherever possible.