Colorful jewels in the terrarium - land crabs of the genus Geosesarma

Crustahunter Chris Lukhaup was so nice and cut us exclusively for this blog a video with habitat recordings and his impressions and thoughts about the wild Geosesarma. At this point again many thanks!

The beautiful, often very intensely colored small land crabs of the genus Geosesarma are not for nothing very popular terrarium inhabitants. Their beautiful colors, peaceful behavior and social interaction are interesting to observe. Most species are crepuscular and nocturnal, but as they become acclimated, the little crawlers can be seen more and more often during the day. Fixed feeding times and feeding places have proven to be effective here. Currently we use our terracotta feeding bowls as feeding places. The Natureholic feeding stations made of coconut shells are also very nice to look at.

Origin of the Geosesarma dwarf crabs

All Geosesarma species originate from Southeast Asia. The individual species are often endemic to individual islands, that is, they only occur there. They usually live in the jungle at and in shallow waters or on very moist ground. They have adapted to land life to such an extent that they cannot live permanently in deep water without sufficient climbing opportunities. Tip: Remedy is the Natureholic Flexible L iane for crab terrariums, which can be cut optimally with pliers and with which you can realize wonderful exit possibilities. Geosesarmas always carry a small water supply in their gill chamber, with which they keep their gills moist and which they renew from time to time, and they also molt mainly in the water. Access to a sufficiently deep water bowl/water area is therefore necessary - 6 cm water height is the minimum.

Socialization

The species of the genus Geosesarma are sociable crabs, which should not be kept alone. However, they do not get along with other species than their own, therefore one should not mix the different Geosesarma species under any circumstances, but consistently stay with one species per terrarium.

Group size and terrarium size

It is recommended to keep a small group - if possible - with a surplus of females. Two females, one male is the minimum size, the only upper limit is the terrarium size. For a group of five to seven animals a standard terrarium with a floor space of 60 x 30 cm is sufficient, for a group of three animals a terrarium with a floor space of 40 x 40 cm is also possible. Larger is of course always possible!

Keeping - the ideal  crab terrarium

You can set up a conventional aquarium as a terrarium, but then you often have the problem that the panes fog up so much that you can no longer really see the animals. Also the ventilation leaves much to be desired. Better is an actual terrarium with ventilation. Attention: the panes must close tightly, the crabs can escape through a slit! They are extremely good climbers and can reach even the higher slits.

Attitude - the water part 

In an aquarium filled with water, these predominantly land-dwelling crabs will not be happy. Even an aquaterrarium with a large, deep water part and only a few, small land parts is not suitable for Geosesarma species. The pretty little pinchers are well off in a terrarium with a deep water bowl or a water part of at least 6 cm depth. Pay attention to exit aids as mentioned above, which can also consist of small stones, pieces of bark, branches ... These are allowed to protrude into the water. There should always be one exit aid more than crabs.

Keeping - the arrangement of the Geosesarma terrarium

It is important to structure the tank well. A very well structured smaller terrarium is much more species-appropriate for Geosesarma crabs than a naked tank of any size! Structure is best brought into the tank by finely branched root wood or cork bark. Terrarium back walls made of coconut fiber are also a great way to bring a lot of structure into the terrarium, can be planted and also look great!(Natureholic coconut fiber terrarium back wall) Please make sure that decoration can not be undermined, it can otherwise fall on burrowing crabs and crush them. Very well accepted are also coconut mats for the walls, which extend the action radius of the crabs again quite strongly and which are climbed very gladly. In the coarse fibers the small claws on the crab feet find good hold, and one can often see the small crawlers scrambling around on the wall. Also coconut caves or clay tubes are gladly accepted as hiding places. A real eye-catcher in the Geosesarma terrarium: Natureholic "Husk" coconut cave

Attitude - the substrate

Special terrarium humus made of coconut fiber or coconut husk is well suited as substrate. Sand is not quite as suitable, can be offered as a mixture with terrarium humus. The substrate should be high enough so that the small crabs can dig their living caves in it, and should be kept permanently moist without becoming moldy. A few brown autumn leaves can serve as hiding places, they are eaten rather rarely.

Husbandry - Plants

Since all Geosesarma species live purely carnivorous, plants are safe from being eaten. So the terrarium can be planted lushly. Please leave some space on the bottom so that the crabs can still dig their living burrows. Plants should never be placed in the terrarium directly from the nursery, as crabs do not tolerate sprays and fertilizers well. Wash the plants very well and leave them in quarantine for at least two weeks. Make them bare root before placing them in the terrarium. All soil residues should be rinsed off well! Our terrarium plants are already watered and can be placed directly into the Geosesarma tanks.

Temperature and humidity

Please not too cool! At an air temperature of 24-28 °C and a humidity of 80-90% the species from the genus Geosesarma feel really well. The humidity can be achieved by daily spraying or by a small spraying system. In addition, the substrate should be kept permanently moist.

What do I need in terms of technology?

A Geosesarma terrarium can be operated with quite low technical effort. Absolutely necessary is of course the lighting, so that the plants grow. Here offer Top lights lamps are the best choice. While conventional lamps often give off so much heat that the 24-28 °C air temperature, which Geosesarma love, is easily reached in the terrarium, it can stay much cooler under LED light (depending on the size of the terrarium). In this case a floor heating cable or a heating stone for terrariums would be necessary. Please always lay wires and cables in such a way that they cannot be reached directly by the crabs and be pinched off or nibbled! Cables leading to the outside can be put out of reach by placing a coconut mat in front of them. A thermometer and a hygrometer are useful for monitoring the air temperature and humidity; there are also practical combination devices from various manufacturers. If you don't want to or can't spray every day, a nebulizer is also a practical tool that also creates dramatic effects.

The food

As a permanent food source we recommend a stocking with live springtails and white isopods. These useful little helpers take care of dead plant tissue and food remnants and are gladly hunted and eaten by the Geosesarma. Geosesarma are predominantly carnivorous crabs, i.e. carnivores. They like to eat earthworms (please cut them into pieces beforehand, living worms disappear in the substrate), Grindal, thawed frozen food like Artemia, brown shrimps and mosquito larvae, freeze-dried insects, unseasoned raw fish, ... Please make sure that the food is as uncontaminated as possible. Food specially made for carnivorous crabs is also suitable. You can offer some unsprayed, peeled fruit or vegetables now and then. Sometimes the crabs also nibble on vegetable food. Not eaten food should be taken out of the terrarium after half a day at the latest. Also food snails are accepted very gladly and can be cultivated in the water area

The reproduction / Geosesarma breed!

Geosesarma land crabs belong to the specialized reproductive type (in English: abbreviated type) and carry few, relatively large eggs. Like all crab species, Geosesarma are separately sexual. In crabs, the abdomen is flattened, carried firmly folded under the head and breastplate (carapace). In males this so-called abdominal flap has a pointed shape like an inverted V, in females the flap is much wider and rounded at the top, i.e. inverted U-shaped. After mating, the females carry their eggs in the slightly open abdominal valve until the small crabs hatch. Since Geosesarma crabs can be quite cannibalistic towards their offspring, we recommend separating pregnant females and removing the adult from the terrarium after the young have hatched. Juvenile crabs also like to be aggressive with each other - lots of hiding places and plenty of protein-rich food will have a positive effect on survival rates. Tip: If the offspring announces itself  with us the use of coarse Kokoshusk substrate proved itself. The substrate creates numerous new hiding places for the young crabs, they hardly ever run into each other. Kokoshusk does not start to mold due to the low PH value!

The species at a glance

In the following we would like to take a closer look at the most common species available on the market and their special features.

Geosesarma dennerle - Vampire Crab

This pretty purple crab with its bright orange to sulfur yellow eyes and the sulfur yellow spot on the back is a very popular and well-known representative of the genus Geosesarma. The species was only scientifically described in 2015, but has been known in the hobby for much longer. Geosesarma dennerle originates from the island of Java, Indonesia. With a carapace width of about 2-2.5 cm it grows quite large for a Geosesarma.

Geosesarma bicolor - bicolor land crab, Krakatau land crab

The bicolor land crab Geosesarma bicolor, also from the island of Java, looks very similar in color to Geosesarma dennerle, but the green-yellow spot on its back is much more intense in color and also more distinct. With a dorsal carapace width of 2.5-3 cm, it grows slightly larger than the Dennerle Vampire Crab.

Geosesarma cf. tiomanicum - Disco Vampire Crab

With up to 2 cm carapace diameter one of the smaller species from the genus Geosesarma. Under intense light the Disco Vampire Crab becomes bright orange on the back and legs, the abdomen is purple, as are the claws. Under less bright light, the crabs are more blue-gray to brownish.

Geosesarma hagen - Red Devil Vampire Crab, Red Vampire Crab

Geosesarma hagen has also been in the hobby for a long time, but was also not scientifically described until 2015. The Red Devil Vampire Crab originates from Java, Indonesia. It is dark brown to black with a bold red dorsal spot and bright red claws and yellow to light orange eyes. It reaches a carapace diameter of up to 3 cm.

Geosesarma pontianak - Mandarin crab

The mandarin crab has - as the name suggests - bright orange claws and legs and a brown-orange body. This pretty little Geosesarma species comes from the island of Borneo (Kalimantan) and grows to only 1.5-2 cm (measured without legs and claws). Originally these pretty little crabs were listed as Geosesarma notophorum, but were described as a separate species Geosesarma pontianak in 2015. Pontianak is the name of the town near which they are found in the wild. When the baby crabs are hatched, the mother carries them around on her back for a few more days. This type of brood care is known in the kingdom of crabs only before this species and from Geosesarma notophorum.

Geosesarma cf. notophorum - White Arm Crab

The White Arm Crab has white claws, red legs, and a reddish brown carapace with a light yellow dorsal spot. It also does not grow very large with a carapace diameter of about 2 cm. As a special feature, the White Arm crab carries its offspring on its back for a few days after hatching, like the Mandarin crab, until the little crabs then become independent.

Geosesarma krathing - the orangeheaded crab

This pretty land crab from eastern Thailand is also quite small, reaching an average carapace width of only 1.5 cm. Its orange carapace with the dark brown dorsal spot, dark brown legs and orange claws is wonderfully pretty.

Geosesarma sp. "Blue Devil Crab" - Blue Devil Crab

The Blue Devil Crab is often sold under the fancy name Geosesarma bogorensis (this is not a valid species name, even though it sounds like it). It has sulfur yellow eyes, its body coloration is purple to bluish, and it has a distinct blue dorsal spot. Its claws are bright purple, and its legs are a slightly darker purple color. At up to 2.5 cm, the Blue Devil Crab tends to grow a bit larger.

Geosesarma sp. "Golden Top" - Golden Top Crab

The Golden Top Crab has no distinct dorsal spot, its entire dorsal side is more or less uniformly colored in shades of yellow, often becoming more intense toward the face. Its legs, like the underside of its body, are dark purple, its eyes are often orange to yellow, and its claws are orange-red to bright red. With a dorsal width of up to 2.5 cm, it is one of the somewhat larger Geosesarma species.

Of course there are many more species in the genus Geosesarma and also many completely undescribed crabs. We are convinced that we have not yet seen everything of Geosesarmidae crawling in the jungles of Southeast Asia. One may be further curious.

Geosesarma cf. rouxi - Roux' Vampire Crab

Geosesarma cf. rouxi has red claw arms and bright red claws. The carapace is beige to yellowish on the upper side and a deep, dark purple on the underside. The legs are also purple. The bright yellow eyes of this small land crab are striking. Juveniles are dark purple throughout and do not change color until they reach sexual maturity. Roux's vampire crab also remains rather small with a carapace diameter of 2-3 cm. Unlike many other Geosesarma, it appears to be omnivorous and exceptionally happy to eat vegetables.

All Geosesarma species in overview:

• Geosesarma aedituens Naruse & Jaafar, 2009
• Geosesarma albomita Yeo & Ng, 1999
• Geosesarma amphinome (De Man, 1899)
• Geosesarma angustifrons (A. Milne-Edwards, 1869)
• Geosesarma araneum (Nobili, 1899)
• Geosesarma aurantium Ng, 1995
• Geosesarma bau Ng & Jongkar, 2004
• Geosesarma bicolor Ng & Davie, 1995
• Geosesarma bintan T. M. Leong, 2014
• Geosesarma cataracta Ng, 1986
• Geosesarma celebense (Schenkel, 1902)
• Geosesarma clavicrure (Schenkel, 1902)
• Geosesarma confertum (Ortmann, 1894)
• Geosesarma danumense Ng, 2003
• Geosesarma dennerle (Ng, Schubart & Lukhaup, 2015)
• Geosesarma foxi (Kemp, 1918)
• Geosesarma gordonae ((Serène, 1968))
• Geosesarma gracillimum ((De Man, 1902))
• Geosesarma hagen (Ng, Schubart & Lukhaup, 2015)
• Geosesarma hednon (Ng, Liu & Schubart, 2003)
• Geosesarma ianthina Pretzmann, 1985
• Geosesarma insulare Ng, 1986
• Geosesarma johnsoni (Serène, 1968)
• Geosesarma katibas Ng, 1995
• Geosesarma krathing Ng & Naiyanetr, 1992
• Geosesarma lawrencei Manuel-Santos & Yeo, 2007
• Geosesarma leprosum (Schenkel, 1902)
• Geosesarma maculatum (De Man, 1892)
• Geosesarma malayanum Ng & Lim, 1986
• Geosesarma nannophyes (De Man, 1885)
• Geosesarma nemesis Ng, 1986
• Geosesarma noduliferum (De Man, 1892)
• Geosesarma notophorum Ng & C. G. S. Tan, 1995
• Geosesarma ocypodum (Nobili, 1899)
• Geosesarma penangense (Tweedie, 1940)
• Geosesarma peraccae (Nobili, 1903)
• Geosesarma protos Ng & Takeda, 1992
• Geosesarma rathbunae (Serène, 1968)
• Geosesarma rouxi (Serène, 1968)
• Geosesarma sabanum Ng, 1992
• Geosesarma sarawakense (Serène, 1968)
• Geosesarma scandens Ng, 1986
• Geosesarma serenei Ng, 1986
• Geosesarma solomonense (Serène, 1968)
• Geosesarma starmuhlneri Pretzmann, 1984
• Geosesarma sumatraense Ng, 1986
• Geosesarma sylvicola (De Man, 1892)
• Geosesarma ternatense (Serène, 1968)
• Geosesarma teschi Ng, 1986
• Geosesarma thelxinoe (De Man, 1908)
• Geosesarma tiomanicum Ng, 1986
• Geosesarma vicentense (Rathbun, 1914)