Starfish

Starfish are part of the same family as sea urchins, ie echinoderms, the name being derived from the Latin words for skin and spines. Usually they have 5 arms radiating from a central disc though there are species, also found here, with many arms.

For something that looks so pretty and inoffensive they are remarkably voracious feeders and highly talented at self preservation and recovery from attack.

Did you know...
...that a starfish can regenerate into its usual 5-armed shape from a single arm attached to the central disc?!

If you see a starfish with irregular arm lengths then it is in the process of regeneration. They can use this same system for reproduction – they just split into two and regenerate, although they also reproduce sexually.

For movement they depend on a water vascular system using many tube feet on the underside of the arms. There is a small eye on the end of each arm though sight is poor, distinguishing only light and dark. This is sufficient however to detect movement. The rough surface of the starfish prevents parasites from encrusting the body and the often bright colour is a deterrent to predators. They are able to feed on creatures larger than themselves because they have two stomachs, one of which can be expelled from the body and wrapped around the prey, digesting it with gastric juices before ingesting it. They can use their water vascular system to force open molluscs such as clams, insert their stomach and digest the clam in situ.

Their diet is largely made up of crustaceans and molluscs although they will feed on any animal, dead or alive, and they appear to love sea urchins.