Common starfish
The common starfish, also known scientifically as Asterias rubens, is a recognizable five-armed echinoderm found primarily along the coasts of Europe and northwestern Africa in the northern Atlantic Ocean. Typically measuring between four to twelve inches across, with arms reaching up to ten inches long, its brownish-orange body exhibits radial symmetry, meaning its structure is organized around a central axis. This starfish is notable for its ability to regenerate lost arms, a remarkable adaptation that aids its survival.
Common starfish are carnivorous, primarily feeding on bivalve mollusks such as clams and oysters, and utilize their tube feet to pry open the shells of their prey. They have a unique feeding mechanism, where they externally digest their food by injecting digestive fluids into the victim's body. Reproduction occurs in warmer months through external fertilization, resulting in the release of millions of eggs into the water. After a larval stage spent floating at the ocean surface, juvenile starfish eventually settle to the seabed, developing their characteristic star shape. While they face predation from various marine animals, the common starfish is not currently considered a threatened species, with a lifespan averaging seven to eight years.
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Common starfish
The common starfish is the common five-armed starfish that comes to mind whenever people think and talk about starfish. Although the common starfish is only found along the coasts of Europe and northwestern Africa in the northern Atlantic Ocean, many other species of starfish in the family Asteriidae inhabit waters around North and South America.
Kingdom: Animalia
Phylum: Echinodermata
Class: Asteroidea
Order: Forcipulatida
Family: Asteriidae
Genus: Asterias
Species: Rubens
The common starfish may grow to be between four to 12 inches (10 to 30 centimeters) across and each of its arms may be up to 10 inches (25 centimeters) long. Its brownish-orange body, like the bodies of other echinoderms, is radially symmetrical. This means its body parts stem from a central axis, or point. Five arms extend from the central axis of the common starfish. If it loses one of its arms, the common starfish is able to produce a new arm. This process is known as regeneration. On the bottom of each of the arms of the common starfish are rows of tiny, tube-like tentacles known as tube feet. The common starfish uses its tube feet to walk and to help pry open certain prey.
The common starfish is found around the coasts of Europe and in the north Atlantic Ocean. This echinoderm, or spiny-skinned creature, is also found along the northwestern coast of Africa. Like other starfish, the common starfish moves along the seabed in search of food. Typically, the common starfish is found from the lower shores to depths of about 650 feet (195 meters).
As a carnivorous, or meat-eating, animal, the common starfish actively hunts for its prey. The diet of the common starfish consists mostly of bivalve, or two-shelled, mollusks such as oysters, clams, mussels, and scallops, but may also include sponges, corals, worms, crustaceans, other starfish, and small fish. The common starfish finds its food by responding to chemical signals which it picks up on its tube feet.
When the common starfish attacks a bivalve mollusk it wraps its body around the tightly sealed shell of the mollusk. It then sticks its tube feet onto each of the shells and pulls the mollusk apart. At the same time the common starfish pushes its stomach out through its mouth and injects digestive fluids into the body of the bivalve mollusk. The mollusk's soft body parts turn into a soupy mixture after being partially digested by the stomach fluids of the common starfish. The common starfish quickly sucks this mixture into its stomach, releases the mollusk's shell, and returns to its normal form on the ocean floor.
Mating for the common starfish takes place in the springtime and warmer seasons. After the male and female common starfish release their sperm and eggs into the water, the over two million eggs are fertilized. This process of external fertilization is known as spawning. Most fish reproduce in this way. After fertilization, a common starfish egg becomes a small, bean-shaped larva with 12 arms. At this stage the common starfish larva floats through the water near the surface for around three weeks. Eventually, it loses its arms and grows three new, stronger arms. At this point the larval common starfish settles to the seabed and begins to develop into an adult common starfish. It grows a starfish bud on the top of its body and begins to develop its five adult arms. A newly developed adult common starfish may be about four inches (10 centimeters) across.
Fish, sea turtles, crab, snails, shrimp, otters, and other starfish, or sea stars, may prey on the common starfish. The life span of the common starfish is between seven and eight years. While many species of starfish may be endangered, the common starfish is not believed to be a threatened species.
Bibliography
“Sea Stars.” National Aquarium, 2024, aqua.org/explore/animals/sea-stars. Accessed 25 Apr. 2024.