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Cardisoma armatum (African rainbow crab) – Species database
#1
Text: Monika Rademacher – Translation: Ulrike Bauer – Photography: Oliver Mengedoht

Scientific name: Cardisoma armatum

Trivial name:  (African) rainbow crab, moon crab, patriot crab

Systematics: Domain: Eucaryota, kingdom: Animalia, subkingdom: Metazoa (multiple-celled animals), Eumetazoa (true tissue), grade: Bilateria, branch: Protostomia, infrakingdom: Ecdysozoa (molting animals), phylum: Arthropoda (jointed-leg invertebrates), subphylum: Crustacea, class: Malacostraca (higher crustaceans), superorder: Eucarida, order: Decapoda (ten-legged crayfish), suborder: Pleocyemata, infraorder: Reptantia, section: Brachyura (true crabs), superfamily: Grapsoidea, family: Gecarcinidae (land crabs), subfamily: Cardisoma, species: Cardisoma armatum

Origin/Range: West-African coast from Cape Verde Islands to Angola

[Bild: DSC_2717.jpg]
more photos:http://www.panzerwelten.de/photos/index....ategory/59[/url]

Description: blue carapace, orange-red legs and claws, claws have white tips and also some blue parts, light-colored abdomen. There is a totally blue-white variant, too.

Sex differences: Typical for crabs, the males have a narrow abdomen and their claws are of different sizes; the females have a wider abdomen (although not as pronounced as other crab species) and smaller claws, both of the same size.

Size: The carapace is 10 to 20 cm wide (most crabs collected from the wild stay smaller though).

Life span: at least 20 - 40 years

Water temperature: 19 to 29 °C

Size of the aquaterrarium/stock: 1 m tank or larger for one crab; have to be kept single

   

Set-up: Terrarium with a water part or an aquaterrarium (aquarium with a land part) with wood, stones and hard-leaved plants; well-structured with lots of hideaways (wood, stones), brown leaves (for concealment and food). In the water sand or gravel, on the land part sand, soil, a mixture or terrarium humus (from our experience this is suited best as it does not tend to mold). The crabs can still burrow in the humus, but they aren't able to dig deep tunnels they could get trapped in sometime Icon_wink. Brackish water is also a possibility.



Food: Typical for crabs, they are omnivores.
• Leaves (the main staple of many crabs in nature; mostly oak and beech are fed, however, all European broadleaved tree leaves are possible, also Indian almond leaves), muck, water plants
• Vegetables/fruit: nearly all vegetables and fruit are suitable (peas, lettuce, cucumber, apple, zucchini, pear, banana, grapes, tomato, Brussels sprouts, bell peppers) except for parsley and beans or other kinds that contain Prussic acid or copper; carrots (boiled); potato and rice (boiled); no citrus fruit due to their high acid content
• Dry food: Catfish tabs, fish (flake) food, food pellets, rabbit, guinea pig and chinchilla food pellets (without copper!), Spirulina tabs, crayfish tabs, Gammarus
• Frozen food: Black, glass and blood worms, Cyclops, brine shrimp, clam meat
• Live food: Earthworms (it's best to cut them into pieces though, or else these worms might burrow in the substrate, possibly also under water, die and rot there unnoticed until it's too late)
• Meat (rarely): Chicken bones with meat rests (rinsed well to prevent too much fat from getting into the terrarium)
• Fish: deep-frozen smelts et.al., tuna fish, sardines, herring etc. fresh or from a can (in their own juice, not in oil)
• Calcium: cuttlebone, smashed eggshells or powdered calcium in self-made food sticks

   
Several rainbow crabs at a pet shop in Duisburg, among them even some of the rarely-imported females.

Behavior: Aggressive towards conspecifics as well as basically any living being smaller in size (or rather, that fits in the claws), they often sit motionlessly on some wood above the waterline or in their holes on the land part for hours or even for days. They like to burrow (in nature they dig over two meter deep tunnels down to the ground water). Like to sit in "knee-deep" water so that their eyes are above the waterline and they can breathe easily. Aquatic and land plants are hardly ever eaten or shredded, however, the crabs might uproot them when walking over or undermine land plants when digging. They like to have their back carapace stroked with a toothbrush, and, when they are very tame, also their claws. They recognize their keeper and can be fed with tweezers or even by hand. By judging the vibrations of the steps they can discern between a person they know or a stranger.

[Bild: DSC_2715.jpg]
"Cookie Monster" Vincent. Icon_wink

Reproduction: When reproducing, the crabs return to the beach, and the females release their larvae into the sea after a good two weeks. There the larvae go through several zoea and megalopa stages before leaving the sea as young crabs and going to live on land. They have not been bred in captivity so far (at Alfred Wegener Institute for Polar and Marine Research in Bremerhaven once some zoea larvae had been reared to the last megalopa stage in order to study the salinity that's best for that purpose. Research report: [url=http://www.awi-bremerhaven.de/Publications/Cue2002a_abstract.html]Morphology of the larval stages of Cardisoma armatum Herklots (Brachyura, Grapsoidea, Gercarcinidae) reared in the laboratory  (engl.).

Socialization: Shrimp, snails (smaller specimens might get eaten from time to time), guppies, neon tetras; no ground-dwelling fish, crayfish or other crabs.

   
Vincent and Quentin staring at each other.

Additional information:
• Females are rarely imported, therefore mostly only males are avaiable. It is said that the African collectors catching these crabs on behalf of pet crab importers or delis believe that it is bad luck collecting the females, as they are the mothers of the young crabs and catching them could endanger the population.

• Currently we are keeping a pair of this species in a 1.50 m long tank with two land parts on different levels. Even though sometimes aggressive behavior can be observed, the male has so far only once lost a leg, on the other hand they mated successfully, and Zoé was berried once. There have been several reports about the female dismembering its male when a pair is kept, and also cannibalism is absolutely no exception.

These crabs are described as solitary by every source, only meeting with a partner during mating season (only Frank Schaefer writes in his book "Süßwasser-Krabben. Aqualog Minis, Band 6 Liebenswerte Minimonster" {ISBN  3-936027-67-6} that Cardisoma armatum alledgedly live in colonies at the beach). We assume that our arrangement works so well because the crabs have land parts of their own and thus cannot widen their territory without leaving it - this has been working out for us for over a year so far).

Dresden Zoo also keeps Cardisoma aramtum.
• An interesting article from "Practical Fishkeeping": Matt Clarke looks at the stunning Rainbow crab, Cardisoma armatum
"Rainbow Crabs"


[Bild: DSC_3370.jpg]
(Our berried and thus very pale) female Zoé.

[Bild: DSC_2735.jpg] Vincent, the colorful male
[Bild: DSC_2708.jpg] Scary: Cleaning his eyes with the claws *g*
[Bild: buddelt2.jpg] Rainbow crabs like to dig a lot.
[Bild: Vincent_TDS_DSC_4929.jpg] Malayan trumpet snails? Yummy Icon_mrgreen
[Bild: DSC_5861.jpg] Rainbow crabs can be fed by hand by their keeper.
[Bild: DSC_0753.jpg] The females' abdominal apron is wider
[Bild: DSC_0826.jpg] Facial field with mandibles
[Bild: DSC_1929.jpg] Eating a pleco
[Bild: DSC_0089.jpg] During mating dances these crabs also like to do cartwheels
[Bild: DSC_4168.jpg] Male crab Quentin has shed and is sitting exhaustedly next to his exuvia for several hours.
[Bild: DSC_4272.jpg] After molting, "soft-shell crab" Quentin looks still rather waxy.
[Bild: DSC_3025.jpg] Rainbow crabs really love to dig.

[Bild: IMG_2002.jpg]
After large digging works going on, berried Zoé is covered by dirt. Icon_mrgreen

THIS SPECIES PORTRAIT as PDF file
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