Do sea stars have eyes on their limbs?


By Angelica Romero Blancas

While sea stars do have an eye at the end of each “arm” scientists are still researching how effective these eyes are and what function they actually serve. Recent research indicates these ‘eyes’ are used to locate reefs where they can safely find food.

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Sea stars are an exotic natural beauty, often possessing five arms, but the number varies with some species have as many as 40. They come in various sizes and striking colors sometimes their bodies are adorned with protective spikes like punk children putting on a tough exterior to protect themselves and survive in the harsh and relentless environment that is the ocean.

As they are not actually fish, the technically-correct term for these animals are sea stars. They have no brains or blood. Instead of blood, sea stars filter ocean water through their bodies. Sea stars function without a brain by using a highly-developed nervous system with most of their vital organs tucked within their arms. They use their limbs and the tiny sensors protruding from them to feel their way and move across the ocean.

Regeneration is one of the most famous abilities that sea stars possess. They can lose a limb if attacked, leaving it behind for their predator, slowly fleeing before growing the limb back. Many lizards also use regeneration, losing inches off their tail when attacked, only to grow it back later. Most sea stars require their central body to be whole in order to regenerate; however, a few species, in fact, have the ability to regenerate themselves from part of a limb.

The sea stars’ limbs also prove to be pivotal for feeding. Despite having little to no eyesight, slow speed, and no brain, sea stars are carnivorous hunters, feeding primarily on mollusks, clams, oysters, sand dollars and mussels. They prey predominantly immobile species, rendering their own slow movement unimportant. Opportunistic hunters, sea stars will eat other creatures and organic material as long as it is an “easy catch.” They will consume snails and injured fish when available as well as sponges, plankton, or coral. Sea stars use their arms to pry apart shellfish to get at the prey’s muscle. Once opened, the sea stars stomach comes out of its body to swallow they prey, pulling it into their body to digest it internally.

Sea stars can live to approximatley 35 years old. They typically breed in the spring and can lay as many as 2.5 million eggs. Pregnant sea stars will feel “plump and spongy” with arms filled with eggs. Sea stars can have distinct genders and mate with each other, they may also change their sex or reproduce asexually. It is generally difficult to see the gender of a sea star and may require close inspection under the microscope to fully find out.


#seastars #starfish #reefs #conservation #TSF