Hello, I'm an expert in marine biology with a focus on echinoderms, which includes sea stars or starfish. Let's delve into the fascinating world of sea stars and their circulatory system.

Sea stars do not have blood in the traditional sense that we associate with vertebrates like humans or other animals. Instead, they have a unique water-based circulatory system.
Their body fluid, which is responsible for the transportation of nutrients and waste, is called hemal fluid. This fluid is not red like our blood and does not contain hemoglobin, the protein that gives blood its red color and carries oxygen.

The hemal fluid circulates through a network of water vascular systems within the sea star's body. This system includes tube feet, which are used for locomotion, feeding, and respiration. The fluid is pumped by a series of ring canals and helps in the movement of the sea star and the distribution of nutrients.

So, to answer your question, sea stars do not have "blood" as we know it, but they do have a circulatory fluid known as hemal fluid that serves a similar purpose.

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Sea stars live underwater, but that is where their resemblance to fish ends. They do not have gills, scales, or fins. Sea stars live only in saltwater. Sea water, instead of blood, is actually used to pump nutrients through their bodies via a 'water vascular system.'read more >>