Home > Tips & Tricks > Harlequin Shrimp (Hymenocera picta) | The Strange Starfish-Eating Shrimp

Harlequin Shrimp (Hymenocera picta) | The Strange Starfish-Eating Shrimp

As regular readers will know, we love invertebrates over here at FantaSEA, and we’ve already discussed many on the blog. None of them are quite as spectacular-looking or wacky as the topic of this care guide, though: harlequin shrimp of the genus Hymenocera.

If you’d like to add a seriously weird shrimp to your tank, keep reading! Below, we’ll have a look at everything you need to know about harlequin shrimp and their care, including where they’re from, their unusual diet, and much more.

Name (Common, Scientific)Harlequin shrimp, painted shrimp, Hymenocera picta, Hymenocera elegans
Minimum tank size10 gallons
Minimum group size2
Temperature72-82 °F
Salinity1.020-1.025
pH8.0-8.4
Difficulty levelIntermediate

Harlequin shrimp description & natural habitat

Taxonomy

Before we start discussing their absolutely bizarre appearance, let’s have a look at what harlequin shrimp actually are. Despite their outlandish looks, they belong to the family Palaemonidae just like many of our other favorite aquarium shrimp. Their genus is called Hymenocera.

Hymenocera is usually considered monotypic, meaning it has only species: Hymenocera picta. However, because there’s a good bit of regional variation in H. picta coloration, some experts split the genus into two. They consider harlequin shrimp from the Indian Ocean to belong to an unrecognized species referred to as Hymenocera elegans.

Description

As for looks, where do we start?! There are many strange-looking marine shrimp out there, but this one absolutely takes the cake. The harlequin shrimp si almost reminiscent of a praying mantis, and we’ve also had people ask if they were baby blue-ringed octopi. Can’t really fault ’em, either: it can be hard to figure out what animal you’re looking at.

These shrimp have large, flat claws and flat eyes. Unlike other shrimp, which tend to have very long and thin antennae, theirs are flat and leaf-shaped. Hymenocera picta has a white body with purplish spots.

The shrimp often named Hymenocera elegans sports more reddish spotting, which is one of the reasons some consider it a separate species. This being said, the color difference is thought by other researchers to be the result of variation in diet—the shrimp taxonomy battle rages on!

Both H. picta and H. elegans, whether they’re different or not, grow to a maximum size of around 2”.

Vintage illustration of harlequin shrimp from Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum
From Annals of the South African Museum (Annale van die Suid-Afrikaanse Museum)

Natural habitat

Harlequin shrimp are naturally found in the Indo-Pacific. Even though they can be locally pretty uncommon, they have a huge range that stretches all the way from Africa to Central America.

In their natural habitat, harlequin shrimp inhabit shallow reefs, usually staying between a depth of 3-100 ft. They prefer the safety of sheltered areas like rock crevices and caves.

Harlequin shrimp aquarium

If you’d like to keep a pair of harlequin shrimp in your own aquarium, keep in mind that these guys are pretty sensitive. High water quality is very important, which means they might not be the best choice for beginning aquarists.

Because harlequin shrimp don’t grow all that large, an aquarium of 10 gallons or up should work fine for them as long as you don’t add any large tankmates. Do keep in mind that large aquariums are easier to keep stable, which is important given these shrimps’ rather messy diet.

Harlequin shrimp are not too picky when it comes to their surroundings. Just make sure the water flow is on the gentler side and provide plenty of hiding spots to help imitate their natural habitat.

Harlequin shrimp compatibility

Harlequin shrimp ♥ harlequin shrimp

This species is naturally almost always found in very closely bonded pairs, which rarely leave each other’s side. Researchers have actually found that harlequin shrimp are less “nervous” in their behaviors when accompanied by a partner, indicating lower levels of stress. That’s why we do recommend getting a pair for your aquarium!

Keep in mind that harlequin shrimp are territorial. If you want to keep more than one pair in the same tank, you’ll have to provide plenty of space.

Did you know? Harlequin shrimp can’t really see very well. They find their mates based on chemosensory cues: females emit pheromones when they molt, which are picked up by males. They do occasionally mess up, causing 6.5% of pairs to be of the same sex.

Tankmates

As for tankmates, harlequins are aggressive towards other shrimp even if they belong to the same species, so those are out. In turn, they are vulnerable to attacks by larger fish species and might become withdrawn when combined with overly boisterous tankmates.

Many aquarists prefer keeping their harlequin shrimp in a single-species set-up or with very docile tankmates. We’d recommend small gobies, blennies, dartfish, and dragonets (like panda gobies, tailspot blennies, firefish gobies, or scooter blennies), ocellaris clownfish, and similar.

These shrimp are reef-safe. They’re highly particular about their food and not interested in eating corals at all.

Harlequin Shrimp (Hymenocera picta) underwater photo

Harlequin shrimp diet

In the wild

Their highly specific diet is probably the most fascinating thing about this shrimp species. Harlequin shrimp only eat starfish and nothing else. Maybe they’ll have a nibble at the odd sea urchin, but that’s it.

Harlequin shrimp hunting behavior is fascinating. Larger starfish might be kept alive for days or weeks at a time while the shrimp feast on their legs. As author Wickler described in 1973, the whole thing is pretty gruesome: “Hymenocera seem to feed exclusively on starfish; they are able to capture even large specimens (…) The shrimp normally turns the starfish upside down and then pierces its epidermis with the first pair of legs which possess sharp and tiny chelae. These pull out internal tissue which is eaten.”

Did you know? The coral-eating crown-of-thorns starfish (Acanthaster planci) is known for damaging coral reefs in much of the harlequin shrimp’s natural habitat. Harlequins do eat these pesky starfish; a 1984 study in Panama revealed that the rate of crown-of-thorns death is highest when the shrimp wound the starfish and it’s subsequently killed off by a worm called Pherecardia striata.

In the aquarium

Their strange food preferences are what makes harlequins more challenging to keep than many other shrimp: you’ll have to be able to provide a constant flow of starfish.

A few points about this strange starfish-based diet:

  • Harlequin shrimp only eat starfish legs. This means that you can keep a bunch of starfish in your refugium and snip off one of their legs for shrimp feeding time; the leg will regrow quite quickly.
  • Asterina starfish, a small species that’s generally considered a pest, is one of the starfish on the menu. Yay! If any of your reef-keeping friends or your local aquarium shops are struggling with asterina, you can ask them to keep them for you after removal from the tank.
  • You can buy starfish in bulk and freeze them. If they’re live, it’s fine if they’re quite large, that just means a longer feast for the shrimp.

Remove any uneaten bits of food after a few hours and keep a close eye on the water values in your tank. You’re likely to have to do more frequent water changes than you’re used to, as pieces of decaying starfish can quickly spoil the water.

Did you know? As with their mates, harlequin shrimp depend on chemical cues to find food. They have chemoreceptors in their antennae that allow them to “smell” starfish.

The demonstration of chemosensory food detection in Hymenocera picta Dana (Decapoda, Caridea), a proposed predator of the crown-of-thorns starfish Acanthaster planci (L)
Colorful harlequin shrimp in the aquarium.

Breeding harlequin shrimp

Yes, it is possible! Breeding most types of marine shrimp, including this one, is considered challenging but not impossible. Harlequin shrimp start out their lives as tiny, fragile larvae, which have to pass through several larval stages and eventually metamorphose before they’re considered “real” shrimp.

According to research, you can tell the females apart from the males by their colored abdomens and the blue tips on their pleopods (back legs). The female is ready to mate after molting, which happens every 20 days or so. After the deed is done, she will produce up to 1000 eggs.

Researchers have found that a temperature between 77-80.5 °F works well for the larvae and will have them metamorphosing in around 5 weeks. Artemia nauplii (newly hatched brine shrimp) make a suitable food choice.

Full FantaSEA marine shrimp breeding guide coming soon, stay tuned!

Conclusion

A beautiful marine aquarium full of wacky and wonderful creatures like the harlequin shrimp is a joy to have in your home. If you’re dreaming of your own tank, don’t hesitate to contact us with your ideas. We design, set up and maintain aquariums for businesses and private clients!

Sources & further reading

Fiedler, G. C. (1994). Larval stages of the harlequin shrimp, Hymenocera picta (Dana). University of Hawai’i at Manoa.

Glynn, P. W. (1984). An amphinomid worm predator of the crown-of-thorns sea star and general predation on asteroids in eastern and western Pacific coral reefs. Bulletin of Marine Science, 35(1), 54-71.

Kawamoto, T., & Okuno, J. (2003). Shrimps and crabs of Kume Island, Okinawa.

Rainbow, P. S. (1974). The demonstration of chemosensory food detection in Hymenocera picta Dana (Decapoda, Caridea), a proposed predator of the crown-of-thorns starfish Acanthaster planci (L).

Seibt U. (1973a): Sense of smell and pair-bond in Hymenocera picta Dana. Micronesica
9, 231-236

Valencia-Mendez, O., Lopez-Perez, A., Martinez-Guerrero, B., Antonio-Perez, V., & Ramirez-Chavez, E. (2017). A new record of Harlequin Shrimp (Malacostraca: Decapoda: Palaemonidae: Hymenocera picta Dana, 1852) in the southern Mexican Pacific Reefs. Journal of Threatened Taxa, 9(8), 10571-10576.

Wickler, W. (1973). Biology of Hymenocera picta Dana. Micronesica, 9(2), 225-230.

Photo of author

Marijke Puts

Hey! I'm Marijke, FantaSEA's resident blog writer. I'm a full-time pop science author, part-time PADI diver and snorkeler, and have been keeping fish since I was a kid. When I'm not writing fish care guides, you can usually find me underwater or trying to figure out how to fit more tanks into my house.

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2 thoughts on “Harlequin Shrimp (Hymenocera picta) | The Strange Starfish-Eating Shrimp”

    • Hallo! Entschuldigung, mein Deutsch ist nicht so gut. Diese Garnelen fressen AUSSCHLIESSLICH Seesterne. Sie werden verhungern, wenn Sie versuchen, ihnen anderes Futter anzubieten. Glücklicherweise haben viele Aquarianer und Aquariengeschäfte Asterina (Gänsefußseesterne). Zum Beispiel: Shop Asterina.

      In deutschsprachigen Ländern gibt es eine große Aquariengemeinschaft, sodass Sie die Seesterne normalerweise auch günstig oder kostenlos finden sollten. Sie können in Ihrem örtlichen Aquariengeschäft nachfragen oder es in Facebook-Gruppen für Aquarianer versuchen. Good luck!

      Reply

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