Starfish belong to the members of the class Asteroids. Starfish have small bear-trap structures known as Pedicellariae, occurring over the body surface.
Although the full range of function for these structures is unknown, some are thought to assist in defence, while others have been observed to aid in feeding or in the removal of other organisms attempting to settle on the surface of the starfish. The Antarctic Labidiaster annulatus uses its large pedicellariae to capture active krill prey. The North Pacific Stylasterias forreri has been observed to capture small fish with its pedicellariae.
On the end of each arm is a tiny simple eye which allows the starfish to perceive the difference between light and darkness. This is useful in the detection of moving objects. Only part of the cells are pigmented (thus a red or black color).
Starfish have rather complex nervous systems, with a distributed brain. They have a network of interlacing nerves called a nerve plexus which lies within, as well as below, the skin. The oesophagus is also surrounded by a central nerve ring, which sends radial nerves into each of the arms, often parallel with the branches of the water vascular system. These all connect to form a brain. The ring nerves and radial nerves coordinate the starfish’s balance and directional systems.
Although starfish do not have many well-defined sensory inputs, they are sensitive to touch, light, temperature, orientation, and the status of water around them. The tube feet, spines, and pedicellariae found on starfish are sensitive to touch, while eyespots on the ends of the rays are light-sensitive. The tube feet, especially those at the tips of the rays, are also sensitive to chemicals and this sensitivity is used in locating odour sources such as food.
Thinking out loud, starfish have a lot in common with my enternal existance. I do at times feel like I’m clinging onto a rock knowing a rough and stormy sea lies a head of me at any given moment; while my external world is proceeding merrily on. Only I know the two incredibly worlds I possess.