Boxer Crabs - also known as Pom Pom Crabs - hail from the warm, shallow coral reefs of the Indo-Pacific region. These fascinating crabs do not possess the broad chelae (claws) seen in the majority of decapods; instead, the chelae are slim with finger-like projections that are covered in small spines, and the crab utilises these to grasp a minute sea anemone in each chelae. The symbiotic anemones are usually either a Bunodeopsis species or Triactis producta. As the crab is unable to defend itself with formidable chelae, it instead moves around whilst holding its anemones out in front of itself. If a predator approaches, it will threaten the aggressor with the anemones, which are, of course, equipped with potent nematocysts (stinging cells). This behaviour is reminiscent of a boxer wearing gloves and sparring, or someone holding a pom pom in each hand, hence the common names. These crabs are also unable to use their chelae to feed themselves, so they rely on the anemones to capture small particles of food from the water column, and then take a proportion of this for themselves using their mobile maxillipeds. A pretty and intricate mosaic pattern adorns the carapace. Since its exoskeleton prohibits growth, the crab must periodically moult when this shell becomes too small, and at this time it will hide away more than usual whilst the new exoskeleton hardens. At this time, it will physically put the anemones down in a safe place, moult, and immediately pick them up again. Any lost appendages will grow back over the course of several moults. The aquarium must be mature and the crabs acclimatised very carefully. As they do not enjoy bright lighting, Boxer Crabs will require a good amount of rockwork in the aquarium that will provide them with plenty of small, shady nooks and crannies to rest and scavenge amongst. Multiple specimens may be kept together as long as there is adequate space and an abundance of hiding places amongst the rockwork so that the crabs are not in constant competition with one another for shelters. Try to ensure that the shelters have moderate current passing over them in order to aid their anemones in filtering particles of food out of the water. Boxer Crabs require small, peaceful tankmates and should never be housed with large, aggressive, carnivorous fishes. Indeed, they are best observed in smaller nano-style reef aquaria living with diminutive, passive companions only. We recommend that when you first introduce your Boxer Crab/s, you do so with the aquarium lights turned off, so that the crab/s have a chance to find a protected spot when the fish cannot get to them. Once the crab/s have found a suitable position, it is less likely that they will be preyed upon. *Never use copper-based treatments in the invertebrate aquarium.*
Most nutrition is taken from the anemones, which are filter feeders. Offer plankton and other particulate matter, small meaty foods such as copepods, baby brineshrimp, vitamin-enriched brineshrimp, and finely shaved Mysis shrimp/prawns/cockle/mussel etc. Observe carefully and you may see the crabs using their anemones to 'mop up' food from the surrounding area.
Boxer Crabs have spawned in the home aquarium, however, the resultant miniscule larvae are extremely sensitive and difficult to rear. These crabs are oviparous - the female broods the fertilised eggs on the underside of her body, where they will remain for around 2 weeks as a large orange/red mass. Just prior to the eggs hatching, the female will retreat into cover, only emerging to release the hatched larvae, which by now will have lost much of their bright colour. Release often happens in dim or dark conditions when the female feels safe enough to venture away from her preferred cave. Some aquarists have observed them climbing up on the rockwork to reach a higher area in the tank before releasing the larvae (which may number several hundred) into the water column, probably to aid in dispersal.
|Sexual Dimorphism||Can be sexed by examining the underside of the crab. Females have a much wider, oval pleon, whereas male crabs have a narrow, tapering pleon.|
|Maximum Size||2.5cm (1")|
|Water Parameters||SG: 1.020-1.025, pH: 8.1-8.4|
|Temperature||Tropical: 23-27 deg C (73-81 deg F)|
|Reef Aquarium Compatibility||Excellent|