When people think of starfish they think of the typical five armed creature as pictured above and that is correct for the majority of species. But the species is very diverse and starfish can have anything up to 50 arms and come in a large variety of shapes as shown by the feather stars on a previous post. There are so many beautiful members of this family that you can see while you visit the Great Barrier Reef.
The starfish uses water to propel itself. Yes you thought that it used all those little “legs” with suction caps to move along. Well they do and they use water taken in through their body to provide suction to those “legs”. This helps the starfish to appear to float or glide across the surface of the water.
Starfish generally eat their food whole and use their stomachs to digest their food. They eat just about anything they can find on the reef including clams, fish, molluscs, small fish, coral and algae. They can also digest food outside their body by excreting their stomachs allowing them to eat creatures much largers then they could through their mouth.
Sea stars have endoskeletons. The top of the starfish is sensitive to light and the bottom of the starfish is sensitive to different chemical compositions allowing them to “smell” food. Another cool fact is the starfish breathes through it’s feet.
Starfish breed a lot depending on species. The can be hermaphrodites, capable of sexual and asexual reproduction, some are born males and later change into females. One common fact is you cannot tell the difference between the male and females unless you see them during spawning. Reproductive organs are contained within the starfish.
Feather Stars (Scientific Family: Crinoids) are one of the most peaceful and beautiful starfish. They are a common and fantastic sight on the Great Barrier Reef. There are over 1800 species of starfish globally living in the shallowest waters down to 6000 meters (20000ft) deep. Feather stars make up only just over 500 species of the entire starfish family.
The feather starfish use this arms to filter the food from the passing currents and then pass it down to there mouth. Very different from the traditional starfish that feeds from the bottom and moves along the ground to feed. The feather star has “feet” called cirri that is uses to append itself to fan coral, or other perches where it can feed from a nice passing current.
They also have many more then the traditional 5 arms associated with a starfish. The amount of arms depend on the species and health of the starfish, most species have around 20 arms while some can have over 200. These arms are covered with a sticky substance which it uses to help catch the passing food and pass it down the stars mouth. It is important not to handle these stars as you can severely disrupt their feeding if they are man-handled.
What eats these starfish, well most fish leave them alone. Maybe they are too peaceful, beautiful or graceful to eat?
They breed by releasing sperm and eggs into the surrounding water. The eggs hatch to produce a larva that after a few days float down to the ocean floor or reef where it undergoes a metamorphosis to the adult form.