[BlueTrend Mini-Class] Sea Star Killer, Most Venomous Pretty Shrimp — the Forever-Faithful Harlequin Shrimp

The Editor says: The harlequin shrimp may look tiny and adorable, but it has earned the nickname "sea star killer" — using clever little tricks to drag sea stars back to its burrow for a feast. But how does such a small creature haul home prey so much larger than itself? Follow BlueTrend and learn about the harlequin shrimp's bag of tricks!

Meet the Sea Star Killer: Basic Introduction to the Harlequin Shrimp

With its distinctive markings, the harlequin shrimp (Hymenocera picta) goes by many nicknames — "poodle shrimp," "clown shrimp," and, because of its fondness for eating sea stars, "starfish shrimp." It typically measures 2–3 cm in length and can grow up to 5 cm at most. Females are generally larger than males.

Their body color is mostly white, patterned with yellowish-brown markings and blue-purple spots edged in black. They sport a pair of large claws — nearly as wide as the body itself yet as thin as a cracker (the left claw is usually larger) — with serrated, swollen, flattened tips that wave through the water like the sleeves of a dancer, making them utterly charming.

They are commonly found in rocky reef waters along Taiwan's coastline, primarily inhabiting the deeper subtidal zone. They tend to hide in reef caves and crevices, so you'll need to look carefully to spot them!

Devoted in Love, Devoted in Diet

Unlike most other crustaceans, harlequin shrimp typically live in male-female pairs. Once two harlequin shrimp meet in the ocean, they stay together for life — quite the romantic and faithful couple, isn't it?

And their devotion doesn't stop at love — they're just as devoted when it comes to food! True to their "starfish shrimp" nickname, sea stars are essentially the only item on their menu; they show little interest in anything else. They mainly prey on members of the families Ophidiasteridae and Goniasteridae, and occasionally take on other large sea stars. The harlequin shrimp uses its claws to snip off the arms of a sea star, then gnaws from the tip inward, slowly dragging the meal back to its burrow to dine in peace.

The Toxins in the Harlequin Shrimp

There's a saying: "The more beautiful something is, the more dangerous it is." It should come as no surprise, then, that the stunning harlequin shrimp carries toxins. What's interesting is that these toxins don't originate within the shrimp itself — they are derived from its food source, the sea star, and converted inside the shrimp's body. As a result, the harlequin shrimp's vivid colors and striking appearance serve as warning coloration, signaling to potential predators to keep their distance. Few creatures dare to eat a harlequin shrimp, meaning it has almost no natural enemies!

A Little Story from BlueTrend

A bonded pair of harlequin shrimp lives together and hunts together. If they're lucky, they manage to drag a whole sea star back to their burrow, where they begin sawing off its arms and savoring them at leisure.

The sea star, however, doesn't just accept its fate — it tries to escape. But with one arm missing, its movement slows considerably, and the relentless harlequin shrimp will drag it back inside the burrow just before it reaches the exit, then continue amputating and eating.

In reality, sea stars have remarkable regenerative abilities, so when a sea star encounters a harlequin shrimp, it may voluntarily shed one of its own arms as a means of self-defense.

Which Relatives Also Have a Taste for Sea Stars?

Besides the harlequin shrimp, two other members of the subfamily Hymenoceridae also share a fondness for sea stars. These relatives are even smaller than the harlequin shrimp — usually under 3 cm — so you'll need sharp eyes to spot them lurking on the seafloor of coral reefs!

Leopard Shrimp　Phyllognathia simplex

Covered in intricate mottled spots, this species is also known as the "leopard shrimp." It is quite rare and seldom seen. It favors environments near the base of coral reefs where sandy substrate is abundant, relying on its complex markings and tiny frame to blend in and hide from predators. While it occasionally feeds on small sea stars, it actually has an even greater preference for brittle stars with elongated arms!

Spiny Star-Eater Shrimp　Phyllognathia ceratophthalma

With its alternating yellow, black, and white stripes, this species is commonly called the "tiger shrimp." Its body is covered in numerous prominent spines, making it easy to identify. The tiger shrimp is not large, and mostly hides in rock crevices at the base of coral reefs. Combined with its nocturnal habits, it is not easy to encounter. It feeds on small sea stars, which it often carries back to its burrow to eat.

What to Do If You Encounter One in the Wild

When people hear that harlequin shrimp are venomous, they sometimes panic — but coming across one in the water poses no danger at all! Their shells do not secrete toxins, so you can safely approach and observe them as long as you don't eat one. That said, when photographing or watching them, please do not move or disturb them — doing so could leave them unable to find their burrow, or separate them from the meal they worked so hard to bring home!

Of course, the most important thing to do is snap a photo and upload it to the species database, so that everyone can better understand the appearance and distribution of these beautiful little shrimp!

Want to Learn More About the Ocean?

Ocean Field Guide — Northern Taiwan

Ocean Field Guide — Nearshore Coral Reefs

Further Reading:

• Harlequin Shrimp Species Database
• 【Taiwan · Northeast Coast Longdong No. 4 / Hemei Elementary School】Dive Site Introduction — The Hidden Lembeh