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Home › Sea Wildlife › Marine › Invertebrates › Crustacean › Shrimps › Harlequin Shrimp

Information and Facts about Harlequin Shrimps

[Phylum: Arthropoda] [Class: Malacostraca] [Order: Decapoda] [Family: Palaemonidae]

Some of the common saltwater shrimps are shallow coral reef dwellers that stand out for being obligate predators and for their patterned colourful bodies.

This page contains some of the lesser-known facts about harlequin shrimps (scientific name Hymenocera picta and Hymenocera elegans).

Harlequin Shrimp Distribution and Habitats

Hymenocera picta are commonly found in the Indo-Pacific regions, the Red Sea, parts of East Africa, and the central Pacific, especially:

• Australia (the Great Barrier Reef)
• Hawaii
• Indonesia (including North Sulawesi)
• Papua New Guinea
• Philippines (e.g., Anilao in Batangas)
• Seychelles (including the Maldive Islands)

Even though you may see them in deeper water, generally harlequin shrimps prefer to inhabit shallow coral reefs, typically between one (1) and thirty (30) metres (100 feet).

They tend to thrive best in microhabitats with patches of rubble or rocky substrates. They are secretive creatures that enjoy the protection of hiding underneath coral heads and ledges during the day.

Characteristics of Harlequin Shrimps

There are about 2,000 different types of shrimp in the ocean, and many of them lead a solitary lifestyle. This is not the case with harlequin shrimps, preferring to find a lifelong mate and live together in monogamous pairs instead.

The overall appearance is unmistakeable, with a body colouration that is mostly white and creams. They also have large colourful and somewhat circular spots - usually pale blue and reddish-brown.

But wait - there's more:

They have ten (10) flattened legs for walking, and the front claws contain 'petal-like' extensions (chelipeds). They use them to pin down and flip over living starfish to eat the soft tissues (especially crown-of-thorns juveniles).

Even though the females are a bit larger than the males, they rarely grow much bigger than five (5) centimetres in overall body length (2 inches).

Pro Tip: Another guide explains more about the fascinating anatomy of shrimp, and how the internal and external body parts work.

What Do Harlequin Shrimp Eat?

It's fair to say this particular species of sea shrimp is one with an extremely narrow and controlled diet. So, apart from sea stars (Asteroidea), these "specialised predators" rarely eat anything else.

In greater detail, the preferred prey of harlequin shrimps are small starfishes as they move around the reef, especially:

• Asterina starfish (common with aquarists)
• Blue sea star (Linckia laevigata)
• Red starfish (of the genus Fromia)
• Sea urchins (although more opportunistic and less common)

Generally, the feeding behaviour of these obligate predator shrimps usually needs both members of the pair to flip over the sea star and immobilise it.

After dragging the kill into their secluded den, they will feed on the soft tissues of the oral surface (lower section) and the tube feet. They feed slowly and often keep starfish alive for several days before finally discarding the remains from their lair.

Fun Fact: If you are learning about keeping fish in captivity as a hobby, and thinking about introducing harlequin shrimps to your aquarium, they will not accept any substitute food sources (e.g., meaty seafood, pellets) because their digestive system evolved specifically for starfish tissue.

How Do Harlequin Shrimps Reproduce?

Both Hymenocera picta and Hymenocera elegans have some specialisations in their reproductive strategies, tied most to their lifestyle traits that involve pair-bonding.

For the most part, monogamous pairs will live and hunt together, and reach sexual maturity within a few months - then they start breeding as long-term pairs.

Here's the thing:

After mating, the female will carry large clusters of brightly coloured eggs, sometimes more than one hundred in each clutch, carefully carried within her pleopods (swimming limbs located underneath the abdomen).

The eggs will hatch into zoea (a form of planktonic larvae) and drift with the natural water movements. During this dispersal, the larvae feed on plankton and they will experience several molts before they find a suitable coral reef in which to settle.

Threats and Predators

Even though saltwater shrimps are small, they are extremely nutritious and a vital food source for many marine species, especially large vertebrate fishes (e.g., groupers, moray eels, and triggerfish) as well as common octopus.

Other contributing factors for a population reduction in some vulnerable areas include certain types of human behaviour (e.g. coral reef decline and destruction, overcollection, and overfishing).

Important: The IUCN Red List of Threatened Species is a comprehensive source of information about the global conservation status of animals, fungi, and plants. Currently, the IUCN lists one of the freshwater shrimps - the Sulawesi harlequin shrimp (Caridina woltereckae) - as "Critically Endangered" (CR).

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