Starfish (Sea Stars)

blue starfish (Linckia laevigata)
Blue Starfish (Linckia laevigata)

Starfish (also called sea stars) are unusual looking animals in that they have five arms that surround a central body. Whereas most starfish species only have five arms a few starfish species have even more.

Starfish are very closely related to brittle stars, but are less agile and have thicker arms.

Starfish are echinoderms and they have no head or centralized nervous system. This doesn't mean they don't have a nervous system - just that it isn't located centrally as in most other animals. The starfish nervous system is spread throughout their bodies and arms.

On the underside of each arm they have tube feet with suckers. They use these to attach themselves to objects to move across the reef.

Starfish occasionally lose one of their arms due to predation or other injury. Most of the time they are able to regenerate the missing arm. In fact, sometimes a starfish arm can regenerate into an entirely new starfish, but usually only if a portion of the central body is still attached to the arm.

Starfish tend to spend a good portion of their time remaining motionless, but are capable of moving quite quickly.

The size and color varies greatly among starfish. They are often yellow or red, but can be many different colors, including the brilliantly colored blue as shown in the top photo.

red knobbed starfish (Protoreaster linckii)
Red Knobbed Starfish (Protoreaster linckii)

Starfish are carnivores and in their natural environment often eat crustaceans and bivalves, such as mussels, clams, and oysters. Starfish are able to use their arms to help them open the shells of bivalves.

Starfish will even sometimes eat smaller starfish! They are not picky eaters. In captivity feed them small pieces of crustaceans and other marine-based meaty foods. You should also have plenty of well-established live rock in their tank for them to feed on.

Their mouth is located in the middle of their body on their underside. They eliminate waste products through a hole in their upper (top) side.

Starfish reproductive behavior depends on the starfish species and can be sexual or asexual, depending on the species.