Pom-pom crabs are a species of small crab that all belong to the genus Lybia. Also known as boxer crabs, these crustaceans are most famous for their signature behaviour of carrying a small, living sea anemone around in each claw — giving them a pom-pom or boxing glove-like appearance.
In the wild, these scuba diving marine life bucket list-worthy treasures can be hard to find due to their small size, timid nature and camouflaged appearance. However, like so many of the coolest and rarest marine animals, with a keen eye and the right know-how, you might be lucky enough to spot one.
Read on to discover 13 fascinating facts about the boxer crabs.

1. Their ‘Pom-Poms’ Aren’t Part of Their Body
When you first see a pom-pom crab, it’s easy to assume their pom-pom-like hands are a fixed and permanent part of their body. However, this is not the case. Each pom-pom is actually an anemone (most commonly) being held in each of the crab’s front legs (claws).
This means all pom-pom crabs actually hatch without pom-poms!
2. They Have a Mutualistic Relationship With Their Anemones
Boxer crabs receive multiple benefits from holding anemones in their claws. Boxer crabs use the anemones to catch food and to ward away predators. In return, the anemones get increased access to food and free transportation.
If concerned or attacked by a predator, a boxer crab will threaten the aggressor using its anemone-covered front legs. This waving action, in conjunction with potential threat of contact with the anemone’s stinging cell-covered tentacles (called cnidocytes), works to deter potential predators.
Additionally, when feeding, the sea anemones can be used like sticky mops, gathering debris and food particles from the surrounding water and seabed.

3. They Don’t Need Anemones to Survive
While their relationship is beneficial to each creature, it is not essential for the survival of either species. There have been numerous observations of boxer crabs substituting anemones for other organisms, such as sponges or corals. Additionally, the anemones do not need to be held by a crab to survive.
4. They Are Small
With a maximum size of 2.5 centimeters (1 inch), boxer crabs are small invertebrates. Because of their small size and timid nature, boxer crabs spend most of their time hiding in crevices and will only come into the open for short periods of time when they are hunting, feeding or reproducing.

5. They Prefer a Specific Type of ‘Glove’
In the wild, the majority of pom-pom crabs choose a certain species of anemone for their ‘boxing gloves.’ Triactis producta is the most common glove (anemone species) of choice for boxing crabs.
6. If They Lose a Glove, They Can Make Another
If a pom-pom crab loses an anemone and another isn’t easily accessible nearby, these crabs have been observed to ‘frag’ their existing anemone (if it’s sufficiently large enough to do so). This means they physically split their existing anemone into two, allowing them to replace their lost glove by actively creating a new one.
7. They Have Several Common Names
Because of their eye-catching appearance and dancer-like movements, pom-pom crabs have been given a number of different common names. These include:
- Pom-pom crab
- Boxer crab
- Boxing crab
- Cheerleader crab
- Mosaic boxer crab

8. They Aren’t Related to the Freshwater Pom-Pom Crabs
Freshwater pom-pom crabs (Ptychognathus barbatus) may share a common name with their ocean-dwelling counterparts, but they aren’t closely related. Unlike the Labia genus pom-pom crabs, which get their name because of the pom-pom-like anemones they carry, freshwater pom-pom crabs get the name because they have pom-pom-like patches of hair on their claws.
9. They Are Omnivores
Wondering what pom-pom crabs eat? The answer is a lot of different things. Like most crabs, boxer crabs are scavengers and will generally consume what is available to them. In the case of boxer crabs, the available food is whatever they catch with their anemone gloves as they wave them back and forth in the water or drag them across the seabed.
A boxer crab’s diet may include algae, mollusks, shrimp, small fishes (dead or alive), and even other crabs.

10. They Are Sexually Dimorphic
Sexual dimorphism means the male and female look different to each other. In the majority of crab species, this means males have bigger claws (used for fighting). However, in the case of boxer crabs, both male and female crabs have similarly sized claws because they are used for holding anemones — not fighting.
Boxing crab sexual dimorphism presents itself in the female’s broader abdomen plate — a physical adaptation used for carrying the several hundred yellow-orange eggs produced as part of the reproduction process.
11. They Have to Drop Their Anemones When They Moult
Because of their hard outer shell (exoskeleton), crabs, including pom-pom crabs, have to shed the outer layer of their skin to grow. This process, called molting, involves discarding the old shell, before the hardening of the newly exposed soft shell underneath.
For pom-pom crabs, things are a little bit more complicated as the process requires them to momentarily put down their anemones. This leaves boxing crabs even more defenceless and vulnerable than most crab species during molting.

12. There is an Endemic Species in Hawaii
Also referred to as the Hawaiian boxer crab (Lybia edmondsoni), this species of boxing crab is endemic to the Hawaiian Islands. Its Hawaiian name is kūmimi pua, which roughly translates as “inedible flower crab.”
13. They Live in the Indo-Pacific Region
Pom-pom crabs live in the tropical waters of the Indo-Pacific region. Boxer crabs’ range extends from the Red Sea and the east coast of Africa to New Guinea and Indonesia. They prefer shallow water with sandy and gravelly seabeds. These areas allow them to hunt, hide and blend in among the coral.

Want to Find a Pom-Pom Crab?
Feeling inspired to get in the water and see a boxing crab with your own eyes? Then it’s time to start planning your next dive getaway. Search for a PADI Dive Resort in the Indo-Pacific region by clicking below or get in touch with the experts at PADI Travel via phone, email or chat for advice and more information.