Aug 20, 2022
Uncharismatic Fact of the Day
Most animals need blood to survive, but not starfish! None of the over 2,000 species of sea star have blood, although they do have a circulatory system. To transport oxygen and nutrients through their body, starfish pump seawater through an opening called the madreporite into their bodies. Starfish also use this system to move by contracting various muscles and forcing water into or out of their limbs.
(Image: A cluster of ochre sea stars (Pisaster ochraceus) by David Job)
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