The Harlequin Shrimp was first scientifically described in 1852. The Harlequin Shrimp has a white body with large light blue spots. The males are slightly smaller than the female.
These are small shrimps, typically 2-5cm in length. It has large claws which are for show only; it does not use them for hunting.
These beautiful shrimps have a very specific diet: starfish. Upon finding their prey, they will overturn it to dine on the starfish’s delicate tube feet. Occasionally they take whole starfish many times larger than themselves. Even the huge Crown-of-Thorns, which has almost no natural enemies, is not safe around these guys. Some adults also feed on sea urchins.
Harlequin shrimps detect their prey using scent. The male and female shrimp overturn the starfish together to disable it. Working as a team, one shrimp methodically snips suction-tube feet from each arm of its prey. Meanwhile, its partner grabs an arm-tip and backs up like a tractor, gradually pulling the sea star over onto its back. This allows them to feed on its delicate tube feet starting at the tips and working inwards. Sometimes they will take the starfish into a dark recess where they can continue to feed for several days. Some even feed the starfish prey, keeping it alive so that they can dine on it later.
Their extraordinary coloration may serve as a warning to possible predators. It is thought that the shrimps incorporate toxins from their prey, making them bad tasting or potentially dangerous to eat.
As shrimp and other crustaceans grow, their exoskeleton does not grow with them and they must form a new exoskeleton to match their new size. During the period between molts they also repair themselves. If an antenna, leg or claw is lost new ones will grow and become evident after molting. It may take more than one molting period to fully repair any damaged or lost limbs.
Harlequin shrimps are fairly rare. When they encounter a mate, they stay together for life forming monogamous, often territorial, pairs. They mate shortly after the female’s molt. The female produces between 100 and 5,000 eggs per season which she tends and cleans until they hatch. The last one seen was around the Phi Phi islands at the dive site “Southern Tip”.