The Red Knob Sea Star (Protoreaster linckii) is a starfish. It is a marine (saltwater) invertebrate, because it does not have a backbone. It is also known as the Red Knob Starfish, the Red Spine Star, or the African Red Knob Sea Star. It is not a fish, so scientists prefer to say that it is a sea star.
The Red Knob Sea Star has five elongated tube limbs, called arms or feet. It has several bright red tubercles on its arms. It has a grey body with red stripes that connect the tubercles.
It grows to about 30 centimetres (12 inches) in length.
The Red Knob Sea Star is native to the Indian Ocean and the Pacific Ocean, in the Indo-Pacific region. It prefers shallow pools and lagoons in tropical coral reefs.
It eats soft corals, sponges, tubeworms, clams, and other starfish. Its mouth is in the centre of the arms on the lower surface. It is a detritivore, which means that it eats detritus found on sponges and algae. Detritus is the decomposing or dead parts of an animal.
It can regenerate its limbs if they become damaged or broken. It can also lose a limb on purpose to confuse a predator. The limb will grow back. This is called autotomy.
Its predators include pufferfish, triton shells, shrimp, and sea anemones.
It is diurnal, active during the day.
It can breed both sexually and asexually. It is diocious, which means that each individual is either male or female. The female releases eggs into the sea. She has about 2.5 million eggs, and most of them are eaten by fish.
The eggs hatch into larvae, which float in the sea for about 87 days before settling on the sand of the ocean floor. The larvae then undergo metamorphosis and change into young sea stars.
The Red Knob Sea Star lives for 7-8 years.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM