2000-10 Harlequin Shrimp

By Denise Nielsen Tackett and Larry Tackett

When I hear the word harlequin, I imagine a court jester bedecked in colorful tights and a mask to conceal his identity. After seeing a Harlequin Shrimp (Hymenocera elegans), it’s easy to see why it takes its name from the jester. But this shrimp is no joke—it’s a voracious predator of sea stars.

Size does not matter to Harlequin Shrimp. I’ve seen a juvenile, barely half an inch long, tackle a Linckia Sea Star many times its size. Sea stars, including the Crown-of-Thorns, make up the diet of Harlequin Shrimp, which locate prey by picking up its scent with their antennae. Adults are less than three inches long and have specially developed mouthparts that enable them to chew through the tough exoskeleton of sea stars.

They use their flattened chelipeds, or pincers, in a unique way to disable their prey. The shrimp grabs the prey’s arm with its legs then raises itself up on its chelipeds, which act as levers. It then flips the star onto its back and accesses the inner tissues by munching on the soft tube feet. They also use their chelipeds to saw off tough bits of the prey and for display purposes.

These rapacious shrimp keep their prey alive by feeding on them from the arm tips in toward the central disk. The star’s only defense is to cast off this arm along with the predatory shrimp. Harle-quin Shrimp often work in pairs—a male and a larger female. They work together to flip over the sea star so both can feast on the prize.

Pairs remain together for extended periods and females release unique chemicals that enable males to recognize their mates. Harlequin Shrimp live in crevices throughout the Indo-Pacific region and are sometimes spotted near the reef dragging their prey back to the burrow. There are two recognized species: H. picta in the eastern and central Pacific and H. elegans from the western Pacific to the Red Sea.