Starfish are fascinating marine animals that play an important role in the ecosystem. If you’re wondering what starfish eat and how they fit into the intricate food web under the sea, you’ve come to the right place.

If you’re short on time, here’s a quick answer to your question: Starfish are omnivorous predators that feed on a variety of organisms like clams, oysters, snails, small fish, algae, coral and even other starfish. Their diverse diet connects them to many parts of the marine food web.

In this comprehensive article, we’ll explore the hunting strategies of starfish, the different food sources they consume, and the creatures that see starfish as prey. By the end, you’ll understand how starfish occupy multiple levels of the food chain and have complex relationships with other species in their ecosystem.

The Hunting Behavior of Starfish

How Starfish Catch Prey

Starfish are carnivorous and use a variety of techniques to catch prey depending on the species. Some starfish are active hunters, moving along the sea floor in search of food. Others take a stealthier approach, remaining stationary and waiting for prey to pass within reach of their arms.

Once potential prey is detected, the starfish will ensnare it using its tube feet which function like tiny suction cups dotting the starfish’s arms. The tube feet allow the starfish to move along surfaces as well as cling tightly while subduing prey.

Starfish diets can vary greatly between species. Some are generalist feeders, eating whatever small invertebrates they can capture including snails, bivalves, smaller starfish, coral polyps, and crustaceans.

Specialist feeders may target specific prey—the crown-of-thorns starfish eats coral polyps while the sunflower starfish prefers shelled mollusks like clams and mussels. To feed on hard-shelled organisms, most starfish have the ability to evert their cardiac stomach out through their mouth to engulf and digest prey outside their body.

Locomotion and Movement

While starfish are very slow by nature, they have developed specialized techniques for locomotion to hunt prey or escape danger. Besides using their tube feet to move along surfaces, starfish can synchronize the water vascular system in their arms to propel themselves forward.

Some species even have the ability to swim by coordinating their tube feet or flexing their arms. The morning sun star (Solaster dawsoni) can travel at a speed of up to 40 cm per minute by swimming.

Another unique quality is the regeneration abilities of starfish—they can regrow entire limbs and even develop into an additional starfish if a single arm becomes detached. This adaptability aids in their survival from injury and predation.

Some starfish like the Pacific blood star (Henricia leviuscula) can intentionally shed limbs as a tactic to evade predators.

Digesting Food Outside the Body

Once prey is captured, most starfish species insert their cardiac stomach into or everting it over prey to digest externally. Digestive enzymes are released to break down tissues into a soup-like chyme which the starfish then draws into its 10 digestive glands by contracting muscles around the stomach.

Waste is later excreted through the starfish’s anus situated on its oral (top) surface. This process allows starfish to consume prey much larger than the size of their mouth opening.

Researchers have recorded crown-of-thorns starfish (Acanthaster planci) dissolving entire chunks of reef coral using this extruded stomach technique. The soft corals are broken down chemically in just 2-3 days despite their calcium carbonate composition.

Such digestive capabilities paired with voracious appetites have allowed these coral predators to devastate up to 95% of coral communities across the Indo-Pacific in outbreak events.

Starfish are Voracious Predators

Feeding on Mollusks like Clams and Oysters

Starfish are well known for their ability to prey on mollusks like clams, mussels, and oysters. Their unique anatomy allows them to pry open the hard shells of these animals and consume the soft flesh inside.

Starfish have tube feet on the underside of their arms that can exert large forces to pull apart the two shells of bivalves like clams and oysters. Once the shell is opened, the starfish extends its stomach out through its mouth and into the bivalve to digest the animal.

Some interesting facts about starfish predation on mollusks:

  • Starfish can eat mollusks up to twice their own size.
  • A single starfish can consume over 50 clams in a year.
  • Invasive crown-of-thorns starfish have caused up to 90% loss of coral reefs by preying on reef-building corals.

Starfish are one of the main predators of mollusks like clams and oysters, having significant impacts on their populations. Their specialized feeding habits make them formidable hunters of these shelled animals.

Hunting Snails and Small Crustaceans

In addition to bivalves, starfish also prey on other small invertebrates like snails, limpets, and crustaceans. Their flexible bodies allow them to access hard-to-reach snails hidden in cracks in coral reefs.

Using their suction-cup tube feet, starfish can pull snails right out of their protective shells. For crustaceans like crabs and shrimp, the starfish will catch them with their arms and pass them to the mouth.

Some interesting facts about starfish predation on snails and crustaceans:

  • Mottled starfish often hunt snails, with each individual consuming 500-700 snails per year.
  • Starfish larvae eat floating crustacean eggs and larvae as their first meals.
  • Small shrimp often flee from starfish, detecting their predatory chemical cues.

Though not as famous as their mollusk feeding, starfish are also active hunters of smaller prey like snails and crustaceans. Their diverse diets allow them to flexibly exploit many food sources.

Consuming Coral Polyps

Coral polyps provide another key food source for starfish species living on coral reefs. Starfish like the destructive crown-of-thorns will climb onto live corals and ever their stomach over the surface to digest the individual polyps.

Interesting crown-of-thorns predation facts:

  • A major outbreak can destroy over 90% of a reef’s live coral cover.
  • Outbreaks may occur when their larvae thrive due to coral reef ecosystem changes.
  • Researchers are working on control methods like targeted injections of bile salts.

By preying on living coral polyps, starfish like the crown-of-thorns can drastically alter coral reef ecosystems. Managing starfish populations is crucial for maintaining reef health.

Eating Sponges, Sea Urchins and Other Echinoderms

Sponges and other echinoderms like sea urchins are also on the menu for some starfish species. The common starfish is known to feed on sponges, using its arms to excavate chunks out of the sponge. Tropical starfish species prey on the tube feet and test of sea urchins.

Even starfish larvae may feast on other echinoderm larvae swimming nearby.

Prey Item Starfish Species
Sponges Common starfish, spiny starfish
Sea urchins Crown-of-thorns, cake starfish
Brittle stars Spiny starfish, common starfish

Starfish are not picky eaters – they will readily consume other echinoderms for nutrients. Their flexible diets and hunting strategies allow them to thrive as voracious predators.

Starfish as Prey

Sea Otters

Sea otters are one of the main predators of starfish. Their diet consists of about 25% sea stars. Using their paws, sea otters pry open the arms of starfish to access the vital organs inside. Their ability to crack open and eat sea stars gives them a competitive edge over other wildlife in their environments.

Large Fish

Certain species of large fish like to nibble on starfish too. Fish such as sheephead, ocean sunfish, pufferfish, and triggerfish munch on sea stars when they get the chance. These clever carnivores slurp up sea stars through their mouth openings on the underside of their bodies.

Crabs and Shrimp

Crabs and shrimp prey on baby starfish called larvae. They use their claws and mouthparts to catch and consume the tiny juvenile sea stars before they grow into adults. In fact, only about 1 out of 1,000 starfish larvae survive to become full grown due to heavy predation.

Sea Gulls and Other Birds

Sea gulls and shorebirds like sanderlings eat sea stars that wash up along the beach. The birds poke around the dried out starfish corpses and scavenge bits of tissue from their ragged arms. Although an unappetizing meal, decomposing starfish can provide birds with sustenance in harsh environments.

As these examples show, starfish face threats from all sides in the wild. Crafty marine mammals, hungry fish, aggressive invertebrates, and opportunistic birds all like to feed on starfish when they can. Avoiding predators makes life tricky for these funky echinoderms!

Starfish are Important to the Ecosystem

Keep Populations in Check

As predators, starfish play a vital role in keeping populations of other marine life in check and preventing any one species from dominating an ecosystem (amnh.org). For example, crown-of-thorns starfish are known to feast on fast-growing coral species, ensuring the slower-growing coral species also have room to thrive.

Without this natural population control, coral reef ecosystems could become dangerously unbalanced.

Nutrient Cycling Through Predation

Starfish are detritivores, meaning they feed on decaying organic material. As they consume dead plant and animal matter, starfish release valuable nutrients back into the marine ecosystem that can then be reused (noaa.gov).

This nutrient cycling enables new organisms to grow, continuing the natural lifecycle. Starfish therefore act as essential garbage collectors of the sea.

In addition, when starfish prey on living creatures like shellfish, the leftovers of their meals get distributed into the sand and water, bringing nourishment to other organisms like tiny planktons, algae, and bacteria.

The predatory habits of starfish thereby contribute to the health of entire marine food chains.

Impact on Coral Reefs

Starfish can have both positive and negative effects on coral reef ecosystems. As mentioned, crown-of-thorns starfish are coral predators, capable of causing widespread destruction. Population surges of these starfish have led to coral cover declining by as much as 95% in affected reefs of the Great Barrier Reef (aims.gov.au).

However, many other starfish species have commensal relationships with coral, meaning they benefit from the coral without harming it. Some starfish even protect the coral by preying on crown-of-thorns when their populations get too high.

So while certain starfish can damage reefs if left unchecked, others play a protective, symbiotic role on the coral’s surface.

Conclusion

Starfish occupy a unique position in the intricate marine food web. Their predatory lifestyle allows them to hunt various prey like mollusks, coral and small invertebrates. At the same time, starfish are consumed by higher-level predators like sea otters, fish and birds.

This complex set of feeding relationships connects starfish to different parts of the ecosystem and maintains balance in ocean habitats. Understanding the dining habits of starfish provides fascinating insights into how marine life interconnects and depends on one another.

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