Pseudosesarma

[Ulli Bauer]

Text: Oliver Mengedoht, Monika Rademacher
Photos: Oliver Mengedoht
Translation: Ulli Bauer

Scientific names: Pseudosesarma moeshi, Pseudosesarma crassimanum, Pseudosesarma bocourti, Pseudosesarma edwardsii

Trivial names: Red-clawed mangrove crab, tropical red crab, red-clawed crab; P. bocourti: big blue, big blue Thailand crab


Pseudosesarma moeschii male

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: Sesarmidae (mangrove crabs), species: Pseudosesarma sp.


Male P. crassimanum (claws are more triangular and pointed and not as round as those of P. moeshi, forehead smoother)

Origin/range: Mangrove woods/coasts of South-East Asia


Nine red-clawed mangrove crabs of the genus Pseudosesarma.

More pics: http://www.panzerwelten.de/v/Krabben_co/Mangrovenkrabben/

Description: Carapace coloration variable with a color spectrum from brown to red, brown, reddish or even blue legs (depending on the species), claws brown or red, some have differently colored tips (white, bright red, yellow). Almost always the claws are of a more intensive color than the carapace and legs. The gill areas and sometimes also the inner sides of the legs are of a more intensive color when the crab is receptive. The males' claws often differ considerably in size, the females have smaller claws.

Sex differences: Typical for crabs, the males have a narrow pointed apron and massive claws of differing sizes, the females have a wider and rounder apron nearly covering the entire abdomen, and smaller claws of equal size.


P. moeschii male.


P. moeschii female.

Size: up to about 4 cm carapace width

Life span: about two to four years

Water temperature: tropical (about 20 to 28 °C, more active from 24 °C upwards)


Dead leaves are the main staple of mangrove crabs in nature.

Tank size/stock: Groups of three (1,2) in an aquaterrarium starting at 54 L (60x30x40cm) – keeping a small group of at least three crabs is highly recommendable. In this group, there should be 1 male and 2 females.

Generally a group should always consist of more females than males, and the owner should keep in mind that only several males can be kept in a larger group if all these males have enough room for staking out their territories in the tank.

Tank set-up: Aquaterrarium (aquarium with a land part) and wood, rocks, sturdy plants; well-structured with hideouts (wood, stones), dead leaves (for concealment and as staple food). In the water, use sand or gravel as a substrate, on the land parts sand, topsoil, a mixture of both or terrarium humus, which is best suited according to our experience due to its low susceptibility to mould. Brackish water is also possible.


Shortly before the molt a white gap forms between carapace (back) and pleon (apron).

Food: Typical for crabs, they are omnivores.
• Leaves (the main staple of many crabs in nature; mostly oak and beech leaves 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) or noodles (uncooked? Don't leave these in the tank for too long a time though, they can be the cause of turbid water and finally lead to a bacteria bloom and oxygen depletion); 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


P. moeshi breaks open a trumpet snail.

Behavior: Even though these crabs form territories they need a (small) group in order to live appropriately. When observing them it becomes clear that their behavior is social.

Several males tolerate each other in the aquaterrarium, given that they have enough room and hideouts. In general, there should be more hiding places than crabs on the land as well as in the water parts. These hideouts have to provide not only a physical border but also screen the individuals from view.

The crabs prefer staying close to potential hideouts so that they can retreat into concealment quickly as soon as a they sense potential danger. However, they can be watched on long tours through their territory during which they rather continuously sift through the soils for food (picking, feeling).


Keeping crabs with crayfish or dwarf crayfish usually ends like here: in the digestive tract of the crabs.

Territorial and ranking fights among male crabs can be observed from time to time, however, they only seldomly lose extremities in the process. These fights often can be characterized as show fights during which each participant shows off the power and size of its claws but does not try to inflict damage purposefully.

There are territorial disputes among the females, too, from time to time, however, this happens more seldomly than among the males. This kind of territorial conflict is of a totally different nature than the fights among the males, as the females settle for successfully chasing away troublemakers without taking a chance with a direct trial of strenght.

The crabs are more in the water than on the land parts, however, many prefer retreating to land when getting ready to molt. In the long run, just having a piece of wood sticking out of the water is by no means sufficient (however, this is acceptable for a transitional period of time or in an emergency), as these crabs also burrow.


Crabs are astounding climbers (make sure the tank is sufficiently covered!) and like to sit upside down or sideways. Even a bare silicone strip is enough to reach the rim of the tank.

Reproduction: They belong to the unspecialized reproductive type; the females carry an egg clutch under their apron for three to four weeks, which consists of thousands of eggs, and then release their larvae in brackish/seawater. There the larvae go through several zoea and megalopa stages before they leave the sea as young crabs and take to the land. They reproduce in captivity, although rarely, you can find an extensive report on our breeding them here:
http://www.panzerwelten.de/forum/thread-712.html


This freshly molted crab leaves its significantly paler exuvia (empty skin).

Socialization: Shrimp, snails (smaller specimens might get eaten from time to time), guppies, non-bottom-dwelling fish, crayfish and other crabs.


P. moeschii male.

Additional information:
• The name of "red-clawed mangrove crab" is used for a group of several different species (in aquaristics mainly Pseudosesarma). Besides Pseudosesarma, among others also Chiromantes and Geosesarma belong to the family of Sesarmidae. Some Sesarmidae only reach a body size of 5 mm, others grow to 5 cm. The species offered in the trade usually reach a size of 2 to 4 cm.


P. edwardsii.

• "Red-clawed mangrove crabs" are a very specialized and highly developed group of the Brachyura (true crabs). Their high tolerance towards varying salinities reflects the variability of their habitats: They live in river deltas, but also inhabit mangrove zones up to 30 km away from the coast.
They have adapted to a semi-terrestrial life very well, they can store water in their gills (left and right of the mandibles), which enables them to breathe on land. This water circulates across their body and is thus enriched with oxygen. When they stay on land for a longer period of time (e.g. when the tide is low), they also have lung-like gills.

Moreover, these Sesarmidae are very able climbers and burrowers. Their burrows, up to 1.5 m deep, can reach down to the bottom water and do not only provide concealment but also temperature regulation and water storage.
In their habitats, these crabs are an important link in the food chain, as they serve as food for millions of birds and other predators on the one hand, and on the other they eat up to 80% of the fallen leaves, which they thus bring into the cycle. They also eat smaller animals they catch with their claws, carrion and fruit.


No argument but just a mating.

They are not colonial like e.g. fiddler crabs, but they do live in groups with small individual territories. They have many intraspecific ways of communication, by claw gestures, by drumming their walking legs on the ground and by placing little dung balls. In most of the cases they only get together for mating after displaying for a short time, when kept in a tank they can be observed to form longer-lasting "bonds" like e.g. making and inhabiting a burrow together.

The most species of this genus are found in South-East Asia, their diversity in America, Africa and Australia is significantly smaller. There are no species of this genus in nature in Europe.


P. moeshi: Territorial dispute of two males

• We are currently keeping 17 adult crabs of several species (P. moeshii, P. crassimanum, P. bocourti, P. edwardsii) in a 120 cm long tank with several land parts on an elevated level, among them also 4 or 5 young crabs resulting from our breeding attempt with P. crassimanum. We might have to correct this stock, however, as these young crabs have successfully grown.

• Most plants in the water and partially also those on the land parts are taken apart and eaten up!


Breeding female with egg paket.


This crab has indeed succeeded in cracking open the lid of a large apple snail.


This (harmless) squabble between two males erupted over bloodworms.

[img]ttp://www.panzerwelten.de/d/100368-2/DSC_7616.jpg[/img]
Only seldomly they share their food with con-specifics.

[img]hhttp://www.panzerwelten.de/d/95196-2/DSC_9848.jpg[/img]
P. bocourti can be discerned from the red-clawed mangrove crabs usually found in the trade by the great number of black parts they have, the brightly red claw tips and purplish-blue areas. This is why they are indeed called blue crab or big blue.


Only very few plants are safe from these crabs, here a female P. bocourti.


Examples for suitable aquaterrariums:




60x30x40 cm (length-depth-height)


120x40x50 cm (length-depth-height)