Starfish Resources

Starfish (also called sea stars) are a fascinating group of creatures that inhabit every ocean. Though they are called starfish, sea stars are not actually fish. They are echinoderms, in the same family as sea urchins. Starfish are common sea-dwellers and are masters of survival. They can be found in warm waters, abysses and even in the Arctic.

  1. Anatomy

    • Starfish commonly have five limbs, but some can possess as many as 40. They are one of the few invertebrates that have an internal skeleton, as well as calcified skin for protection. Starfish do not have a traditional circulatory system. Instead they have a water vascular system that uses seawater to transport nutrients through their bodies. This vascular system is also what allows the starfish to move by forcing water through its body in a hydraulic-like fashion.

    Eating Habits

    • Mussels are a preferred food of the sea star.

      A starfish's diet consists mainly of mussels and sea worms. One of the strangest traits of a sea star is its ability to consume food outside its body by extruding its stomach through its mouth, covering its prey. The stomach then secretes enzymes that liquefy the prey; finally, the starfish retracts its stomach after digestion is finished.

    Life Cycle

    • Starfish larvae subsist on plankton until they are large enough to hunt invertebrates.

      Sea stars reproduce externally by releasing clouds of gametes into the water . Each gamete contains half of the DNA for a complete starfish. When these cells fuse, a larva is created. The larvae float freely through the water feeding on plankton until they reach maturity at about 2 years of age. Though typically starfish live to be about 10 years old, it is not uncommon for some species to reach 35 years of age in the wild.

    Regeneration

    • One of the traits the sea star is most famous for is its ability to regenerate parts of its body. Because a starfish does not have a central nervous system, each arm can act as a separate entity. This means the entire organism will not die if it loses arms, or even the majority of its body. In fact, in some cases sea stars are able to regenerate their entire body from a single limb.

    In Aquariums

    • Due to their oddball looks and fascinating traits, starfish have become very popular among saltwater enthusiasts. Not only do starfish make a visually striking addition to an aquarium, they also play an important role in maintaining a healthy aquarium environment. Most starfish scavenge the bottoms of tanks, feeding on leftover food that can otherwise cause unhealthy water conditions. Starfish also sift through the sand, aerating it so that beneficial bacteria can thrive.