Hymenocera picta, commonly known as the harlequin shrimp, is a species of saltwater shrimp found at coral reefs in the tropical Indian and Pacific oceans. It is usually considered the only species in the genus Hymenocera, but some split it into two species: H. picta from the central and east Pacific where the spots are deep pinkish-purple with a yellow edge, and H. elegans from the Indian Ocean and west Pacific where the spots are more brownish and have a blue edge. They reach about 5 centimetres (2.0 in) in length, live in pairs and feed exclusively on starfish, including crown-of-thorns starfish. It does seem to prefer smaller, more sedentary starfish, but as these generally are not sufficiently numerous for its needs, it commonly will attack Acanthaster, both reducing its consumption of coral while under attack, and killing it within a few days.
Harlequin shrimp's only source of nutrition comes from starfish. They are very skilled at flipping over the slow starfish on its back, and eating the tube feet and soft tissues until it reaches the central disk. They, usually one female and one male, use their claws to pierce the tough skin and feeding legs to help them maneuver the starfish. Sometimes the starfish will shed the arm that the shrimp attacked and regrow (the shrimp can then re eat it), but it is usually too wounded to regrow. They may also feed on sea urchins but that is rare and only if they're very hungry because they have tube feet as well.
The Harlequin moves at a very slow pace and in waves. It also may have toxins from its prey (the starfish) which could make it distasteful and potentially dangerous for predators. The shrimp also moves its claws almost constantly. When it comes to males and females, the females are larger and have colored abdominal plates unlike the males. "The female produces between 100 to 5,000 eggs per season depending on environmental factors." The male and female are often seen together in the wild and work together to not only reproduce but also eat food.