Harlequin Shrimp are a gorgeous addition to any tank. These brightly colored crustaceans are highly-evolved hunters adapted to one prey, starfish. For those comfortable watching nature take its course, a single harlequin or mated pair can skillfully overtake and consume a starfish more than twice its size!
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Harlequins have sensitive antennae used to smell starfish. Once detected, the shrimp will close in on the starfish. If your tank has a mated pair, they will attack in unison. Starfish are large, slow-moving creatures with suction-cup-like feet attached to their extremities that are used to hold onto coral and crawl.
The shrimp will overtake the starfish and then use its claws to dig underneath its prey and flip it over. Once upside down, the starfish is essentially immobilized. From there, the shrimp use their claws to open up the starfish’s arms, exposing the soft tissue and gripping cups.
The shrimp often drag the starfish away at this point to their cave or hiding spot to feast in private, free from scavengers or potential predators. Harlequins methodically devour the shrimp from its tips to its center. This cruel practice keeps the starfish alive, nourishing the shrimp for as long as possible.
Unfortunately for starfish, their only defense is to detach a limb and try and escape. While this method can be effective, it leaves the starfish vulnerable to later attacks while lost limbs regrow. Harlequins will feast on the detached limb.
Starfish of all species release a poisonous toxin that repels many predators, but Harlequins adapted to this defense mechanism. The crustaceans seem immune to the substance, and some theorize they absorb it. The shrimp then uses the toxin as a defense mechanism, like an aquatic insect repellant.
Author Note: While Harlequins are not vulnerable to starfish, they generally will not eat brittle starfish, sometimes called serpent starfish, unless they cannot access another food source.
The Perfect Meal
Harlequins will eat almost any starfish they encounter. Chocolate chip starfish are usually the best option for feeding captive Harlequins because they cost about $10 and provide meals for a week or more.
These types of starfish can harm coral since it is part of their diet, so monitor feedings to ensure the shrimp consumes its prey before it damages your reef. Harlequins will also hunt and devour the parasitic Asterina starfish, a hard-to-eliminate scourge on reef tanks.
The exact feeding time will depend on the size of your Harlequin and if you keep a single shrimp or pair. Generally, a medium-sized starfish can feed one Harlequin for one to two weeks.
You can extend this time by isolating starfish in a separate tank and offering your shrimp one limb at a time. This staging system allows the starfish time to regenerate its missing limb if properly fed and housed.
So now you know, Harlequin Shrimp look cute and maybe even funny but they are predators of one of the most beautiful animals in the entire ocean, starfish.