How many stomachs does a sea star have?
Answer
Two
A sea star has two stomachs: a cardiac stomach and a pyloric stomach.
The cardiac stomach is the larger, lower stomach. A sea star can push it out through its mouth and place it over prey, allowing digestion to begin outside its body. This is especially useful when feeding on bivalves such as mussels and clams, whose shells may be too large to swallow whole.
After partial digestion, the food is drawn into the pyloric stomach, where digestion continues. The pyloric stomach connects to branching digestive glands that extend into the sea star’s arms and help absorb nutrients.
Sea stars do not have a centralized brain; instead, they coordinate movement and sensing through a nerve ring and radial nerves. They also are not fish: their closest living relatives include sea urchins and sea cucumbers, and they belong to the echinoderm group. The name “starfish” remains common, although “sea star” is scientifically preferred.