Sea stars, commonly known as starfish, are marine invertebrates belonging to the class Asteroidea. These creatures are recognized by their radial symmetry, often displaying five or more arms radiating from a central body disc. Found in all the world’s oceans, sea stars are part of the phylum Echinodermata, meaning “spiny skin.”
The Specific Interaction with Shrimp
The question of whether a sea star consumes shrimp depends on the sea star species and the shrimp’s circumstances. Healthy, adult shrimp are generally not a primary food source because sea stars are slow-moving predators and scavengers. They primarily target prey that is sedentary or unable to escape quickly. However, many sea star species are opportunistic carnivores and will readily scavenge any vulnerable animal matter, such as shrimp that are dead, weak, injured, or newly molted. While instances of sea stars preying on healthy, fast-moving shrimp are rare in nature, keepers sometimes feed frozen shrimp to larger species in home aquariums.
How Sea Stars Consume Their Prey
Sea stars consume prey using a distinctive method that allows them to eat items much larger than their small central mouth. When feeding on shellfish, the sea star uses hundreds of tiny, suction-tipped tube feet to secure and pry open the shells of bivalves like clams or mussels. Once a gap is created, the sea star performs stomach eversion, pushing its cardiac stomach out through its mouth and into the shell opening. Digestive enzymes are secreted onto the soft tissues, liquefying the meal outside the body. The resulting partially digested material is then absorbed by the stomach before it is retracted back into the central disc.
Primary Food Sources of Sea Stars
The typical diet of a sea star categorizes them as generalist predators and scavengers of the seabed. Their main food sources consist of slow-moving or sessile invertebrates that cannot easily escape their slow approach. They are extremely effective at consuming bivalves, such as oysters, mussels, and clams, utilizing their stomach eversion mechanism. Many sea stars are also detritivores, actively feeding on organic debris and decomposing material on the ocean floor. The diet varies significantly across the nearly 2,000 known species, which include specialized feeders:
- Bivalves (oysters, mussels, clams)
- Small snails
- Polychaete worms
- Sponges
- Various microorganisms
For example, the Crown-of-Thorns Sea Star (Acanthaster planci) specializes in consuming coral polyps, while other species are filter feeders, capturing phytoplankton from the water column.