Boxer Crab – Detailed Guide: Care, Diet, and Breeding

The Boxer Crab (Lybia tesselata)

In this guide, I will discuss the Boxer Crab’s appearance, behavior, dietary needs, tank conditions, ideal tank mates, breeding and much more.

The Boxer Crab (Lybia tesselata), also known as the Pom Pom Crab is a fascinating little crab that posses a unique symbiotic relationship with the anemones on their claws that form the neat appearance of having boxing gloves in front of the body in a defensive or aggressive position. They usually advance first the left claw and then the right one, an action resembling the “left-right combination” of a boxer.

Suitable for both beginners and experienced aquarists, it is one of the most peaceful saltwater crabs, therefore, it can be a perfect addition to small or nano tanks. They are safe to have around your coral reefs as well, so these are a species you dont have to worry about.

Not only are this species of crabs very simple to care for, but they are also extremely interesting and fun to watch in your tank.

Quick Notes about Lybia tesselata

Name Boxer Crab
Other Names
Boxing Crab, Pom Pom Crab, Pom Pom Boxer Crab, Cheerleader Crab, Mosaic Boxer Crab, Mosaic Anemone Crab, Lybia Crab, Hawaiian Boxer Crab
Scientific Name Lybia tesselata
Tank size (minimal) 5 gallons (~20 liters)
Keeping Easy-Medium
Breeding Difficult 
Size 2.5 cm (~1 inch)
Optimal Temperature 25 – 28°C  (~75°F – 82°F)
Water type SG = 1.023 – 1.025
Optimal PH 8.1 – 8.4 (7.5 – 9)
Optimal KH 8 – 12
Nitrate Less than 20 ppm
Diet Omnivore/Carnivore
Temperament Peaceful
Life span up to 5 years
Color Form Yellow to orange-red spots bordered with dark brown or black

Official Name of the Boxer Crab

This species got its name for the live-color pattern on its carapace, consisting of closely fitted polygons, mostly triangles, as in a mosaic or in tile-works. Tessella is a small cubical piece of clay, stone or glass used to make mosaics.

Origin of the Lybia Tesselata

Found in shallow waters in the tropical Indo-Pacific region from the Red Sea and East African coast all the way to New Guinea, it sits on sandy seabeds and coral reefs where it can utilize its unique coloring and pattern to blend in and camouflage itself from potential predators.

Note: There are some records of Lybia tesselata particularly from the Hawaiian Islands. Well, they are erroneous and are actually for a closely related species, Lybia edmondsoni (Hawaiian Boxer Crab).

Description of the Lybia Tesselata

The Boxer Crab (Lybia tesselata) without one anemoneBoxer Crabs only grow to be about 1 inch (2.5cm) wide. Their carapace is a trapezoid shape and marked with different geometric regions forming a stained glass-like appearance. The eyes are relatively big. The legs are prominently banded with thin black lines and are also spangled with small, luminous white spots. Compared to long legs, their front pair of claws are thin and short.  These claws have effectively lost their ability to function in a typical crab manner, as they are too slender and feeble, which makes them ill-suited for defense. However, crabs adapted to hold live sea anemones in each of its claws, which can be used in symbiosis for food gathering and/or defense.

Interesting fact: The claws are no longer used for taking food, a task which has been taken over by the very mobile third maxillipeds and to the pereiopods, specifically the first pair of walking legs.

Note: A sister species, Lybia edmondsoni (Hawaiian Boxer Crab), basically, is a smaller version of the Lybia tessellate. They grow to an average width of about 10 – 15 mm (about 0.5 in).

The Lifespan of the Lybia Tesselata

Nobody knows for sure how long Boxer Crabs can live. In captivity their lifespan range from 2 – 5 years. Some aquarists say that their crabs lived up to 6 years. I believe that it really depends on the conditions you are keeping them, how well you feed them and the size they are when you get them and how stressful your aquarium environment is for them.  

Boxer Crabs lived most in an aquarium containing low competition and the absence of various larger animals. Which is why it is recommended for smaller aquariums to boost its chance of survival.

The Behavior of the Lybia Tesselata

Until Boxer Crabs get used to the daily life of your aquarium, they are actually very shy and easier to find at night when the lights go out. This lifestyle is probably due to their small size, and the fact that many predators could take advantage of them.

Throughout the day many like to hang out on corals or under rocks, hiding away from their tank mates. When night falls, however, they are more likely to patrol the dark tank and you can see them swaying the anemones side to side to collect food from the water column.

Although Boxing crabs are quite peaceful, they are not completely pushovers. In some cases, when they are about to fight, Boxer Crabs can even jump at the adversary. However, in most cases, they do not injure or kill each other.

Although Boxer Crabs are not diggers in its true sense, they can push out some sand (or small rock) to build their caves underneath some Live rocks.

Lybia Tesselata and Anemone Partnership

This species carries a small sea anemone, usually Bunodeopsis spp. or Triactis producta. This symbiosis serves for feeding and defense.

Note: Triactis producta is one of the most dangerous species of venomous sea anemones. The symptoms of stings to bare skin include pain and swelling, occasionally accompanied by a pigmented and blistered lesion, with prolonged sensitivity to the sting site.

At the same time, advantages for the anemone include reaching new sources of food and being supplied with extra oxygen due to the crab movements, while disadvantages might include being robbed of its food by the crab.

For example, in a laboratory study, they were observed stealing up to 100% of the food acquired by the anemone. By doing so the crabs regulate the food intake of their sea anemones, and consequently control their growth, maintaining small size sea anemones for their use.

As I have already said, Lybia tessellate became so dependent on the anemone that their claws cannot effectively grasp other objects or opponents during contests, even when the crabs are deprived of anemones.

Even more, according to observations, crabs without anemones gathered Artemia using their first walking legs, shoveling the food toward their mouth appendages.

Some interesting facts about this symbiosis:

  1. If they lose one of the anemones, crabs will split single anemones into two smaller individuals, inducing asexual reproduction. Each piece of “split” anemone later regenerated giving the crab a complete anemone in each chela. Seventeen out of the twenty-two crabs holding a single sea anemone split it within 6 days after the removal of one of their two sea anemones.
  2. When they fight with each other, they try not to use it to prevent anemone damage or removal by the opponent. They hold them away from opponents almost all the time. As a result, its fighting behavior is more ritualized, with minimal contacts between opponents.
  3. Foxing crabs do not share with their anemones peacefully.
  4. Smaller crabs without sea anemones are not afraid to initiate the fight. Surprisingly, according to the experiments, in all instances, they managed to come away with a sea anemone fragment or a full sea anemone! Despite the great difference in size, it manages in much the same way as larger crabs to succeed.
  5. Even when Lybia tessellate molt, they try to get their anemones in their claws, despite their still soft exoskeleton.
  6. the Lybia larvae hatch from their egg without sea anemones, They presumably acquire their sea anemones sometime after settling from the larval stage.
  7. If the Boxer Crab loses its anemone, it can substitute it by taking something else. Aquarists saw them taking a Yuma, small polyps, zoos, and even aptasia!

Molting Lybia Tesselata 

Like all other crab species, Lybia tesselata also molts. Actually, this is the most dangerous process for any crab, shrimp or crayfish (you can read more about it here). Therefore, it is absolutely crucial to provide your Boxer Crab with plenty of hiding space in your tank.

During the molting process, they become very defenseless, as they are forced to drop the anemones from their claws to shed their shells. If you have the opportunity to see it, they try to do this process very quickly. They’ll wiggle out of their shell and grab the anemones in both claws for defense. Until their new shell hardens, they will hide away under rocks and other formations to protect themselves from potential predators.

During the molt (and few hours after) they are vulnerable to creatures you would otherwise not have considered a threat before.

All shrimp species need adequate calcium supplements and trace minerals in the molting process. I highly recommend reading my article “How to Supplement Shrimp and Snails with Calcium”.

Sexing Lybia Tesselata

Sexing Lybia TesselataAlthough sexing is the same as other crabs it can be difficult because of their small size. You can differentiate the gender by the shape of their abdomens. Males have a narrow and slimmer plate while females have a broad plate on their belly.

In many decapod crustaceans the claws are more developed in males, probably contributing to differences in fighting behavior between genders. Unfortunately, in Lybia tesselata species, this method cannot be applied because of covered claws.

In addition, biologists reported that there is no sexual dimorphism which is directly involved in anemone holding.

Feeding Lybia Tesselata

They are scavengers and do fine just eating detritus in the tank. Boxing crabs use their anemone partners to their advantage, helping mop up food, which feeds them and the anemones. Therefore, if you feed somebody else in the tank, you do not really have to feed them, unless you really want to.

Lybia tesselata is an omnivore (with meaty preference) and seem to eat everything – squid, mysis shrimp, brine shrimp, copepods, frozen foods, plankton, rotifers, sinking pellets, etc.

Keep in mind that while the Boxing crabs are peaceful, they can be quite aggressive when it comes to food.

Is Lybia Tesselata Reef-Safe?

Yes, they are. There are no reports of these crabs causing problems with corals. They will not harm corals in any way.

Keeping Lybia Tesselata

Taking care of the Boxer crab is relatively simple. They are amazingly resilient as aquarium inhabitants. They do not need strong lighting or a high current.

In the wild, these crabs were found under basalt rocks and coral rubble of various sizes in subtidal locations. Therefore, our task is to replicate their natural environment. Make sure to have plenty of little nooks, crannies, and caves for them to hide and lurk. Provide them with Live rocks, and rubble. They will not be happy in a bare bottom tank, but as long as it has a place to hide, it will get by.

The minimum recommended tank size for Lybia tesselata is 5 gallons. The bigger the tank, the better it may be to maintain water parameters. The only downside is that in big tanks, these small crabs will be lost and you probably will not see them for a long time. In addition, in bigger tanks, it is harder to find them to spot feed if you decide to do that.  Since these species are so small, it is easier to keep on eye on them and make sure they’re getting their food in a smaller tank.

Important: Before putting them in your tank do not forget to acclimate them (read more about it). 

Basic Tank Equipment (links to check the price on Amazon)

Breeding Lybia Tesselata

Lybia tesselata are oviparous, meaning the female carries around the eggs they are fertilized and hatch completely outside. The number of eggs can reach several hundred.

Female of The Boxer Crab (Lybia tesselata) with eggsThe eggs are a yellow-orange clump on their tails and remain that way for 13-15 days. During this time, the female will consume more food and be out in the open more making them more susceptible to predators.

Around three days before the eggs are to hatch the female Lybia tesselata will retreat back underneath rock formations until the larvae are hatched. Once it is time, the female will ascend a rock formation and begin releasing the larvae. This process can be very time consuming, releasing them for several hours.

It is larvae are planktonic. It means that they have to complete metamorphose to become tiny copies of their parents.

So far there have been no reports of successful breeding in captivity. The only information that I could find is that:

  1. Lybia tesselata larvae are voracious feeders and exhibit hunting behavior (ciliates).
  2. Larvae need constant feeding (daily).
  3. They are attracted to light after hatch. Use this trick to transfer them into a rearing setup.
  4. Rotifers and phytoplankton are not enough. Supplement the diet with enriched artemia.
  5. Larvae start to settle on the bottom when they are 10 – 12 days old.
  6. The rearing setup requires the same water parameters.
  7. Do not use any rocks or decorations – just a bare bottom with the heater and airstone. You will need to do frequent siphoning out of uneaten food and waste.

Lybia Tesselata and Suitable Tankmates

Although the Boxer Crab can use these anemones in self-defense, in some cases, it is still not enough. You just need to be wary of obvious predators that will attack and eat crab

Prone to being eaten by a number of carnivorous fish species, but some may be deterred by its stinging anemones. Large dottybacks, hawkfishes, wrasses, sand perches, and puffers may attack them. Actually, they do not like fish not matter what kind. As a result, they tend to hide at day and out at night to feed.

Coral banded shrimp, Pistol shrimp, and, sometimes, Hermit crabs may harass Boxing crabs.

Sexy shrimp, snails, porcelain crabs, Emerald crabs, cleaner shrimp (Peppermint shrimp, Red Fire shrimp, Skunk Cleaner Shrimp) usually do not mess with the Boxing crabs.

Note: It is a very rare scenario but I need to mention that not all Lybia Tesselata have a shy demeanor. Several aquarists complained that fully-grown Boxing crabs surprisingly went in “Rogue mode” and start harassing and even killing! They attacked and killed some snails, shrimp and even other Boxing crabs.

Conclusion

The Lybia tesselata is a great addition to your aquarium. They do not need any special tank requirements or extra feedings. Boxing crabs are reef-safe and peaceful unless antagonized. So they are sure to get along with their tankmates unless you pair them with aggressive species.

They do become less shy over time. All in all, this is an ideal invertebrate for a nano tank.

References:

  1. The Polydectinae Dana, 1851, of the Philippines, with description of a new genus for Lybia hatagumoana Sakai, 1961 (Crustacea: Decapoda: Brachyura: Xanthidae). Zootaxa 3052: 51–61 (2011)
  2. Hoover, J.P. (2007).Hawaiian Sea Creatures. Mutual Publishing. Karplus, I., Fiedler, G. C., & Ramcharan, P. (1998). The intraspecific fighting behavior of the Hawaiian boxer crab, Lybia edmondsoni– Fighting with dangerous weapons? Symbiosis, 24, 287–301.
  3. Schnytzer et al. (2017), Boxer crabs induce asexual reproduction of their associated sea anemones by splitting and intraspecific theft. PeerJ 5:e2954; DOI 10.7717/peerj.2954
  4. Bonsai anemones: Growth suppression of sea anemones by their associated kleptoparasitic boxer crab. Journal of Experimental Marine Biology and Ecology 448 (2013) 265–270
  5. A review of the carrying behaviour in brachyuran crabs, with additional information on the symbioses with sea anemones. The Raffles Bulletin of Zoology 1995, 43(2):377-416
  6. Noël P., 2017. La mélie damier Lybia tessellata (Latreille, in Milbert, 1812). In Muséum national d’Histoire naturelle [Ed.], 4 janvier 2017. Inventaire national du Patrimoine naturel, pp. 1-9, site web http://inpn.mnhn.fr
  7. Report of Stingings by the Sea Anemone Triactis Producta Klunzinger. Journal Clinical Toxicology Volume 3, 1970 – Issue 4.

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