Geosesarma

Geosesarma:

Geosesarma is a medium to large sized genus of 68 species of Sesarmidae crabs who exhibit a terrestrial forest dwelling lifestyle located predominantly in Indonesia, Sulawesi, and Java (Worms, 2022; iNaturalist, n.a.). They are found along forest streams, banks, on plants, under rocks, and on the forest floor where they live as efficient hunters utilizing their quick movements and strong chelae or claws. 


Commonly known as Vampire Crabs, Geosesarma are the easiest Brachyuran and or Sesarmid freshwater crab to keep, rear, and breed in captivity. 

They can be kept quite simply in tub-type paludarium setups with static water features or in quite elaborate paludariums with active water features and filtration setups, and the TGD Team has found they can do well either way. 


Geosesarma are genus of small crabs whose carapace typically is between 10-15mm, or .4-.6in, in width while leg span can be variable between species (Orin McMoningle, 2018). Physically, Geosesarma are visually striking crabs with brightly colored and patterned carapaces, chela, and legs. Geosesarma also have large stalked eyes with an incredible number of ommatidia leaving this group of arthropods with incredibly sensitive and responsive eyesight to movement of predator and prey. Some species are capable of breeding before reaching full size, around 75% of full size, such as G. hagen and G. tiomanicum, and potentially others yet to be documented (McMonigle, 2018).    


There is quite a lot of misinformation surrounding the keeping of decapod crabs in captivity but the TGD team has found they can be simpler than previously thought and hopes to shed light on the correct husbandry and best practices of this amazing group of arthropods! 


You can use the navigation bar drop down menu on the side of the screen to navigate to species or you can naviagte from here to the species you are intrested in below: 

Geosesarma bicolor

Geosesarma dennerle 

Geosesarma hagen 

Geosesarama notophorum 

Geosesarma pontianak 

Geosesarma rouxi 

Geosesarma tiomanicum 

Size: Size descriptions will always be listed for carapace as width x length as follows Ng (1988). 

Javanese Geosesarma G1 Gonopod Morphology 

Ng & Wowor (2022) note that there appears to be a correlation between the structure of the G1 gonopod and the location and altitude above sea level for the Javanese Geosesarma. There descriptions are as follows: 

The lowland species occurring between 0-100m above sea level like G. bicolor, G. dennerle, and G. hagen, from westernmost coast and coast south of Central Java Province respectively, have a G1 that is more long and slender with the chitinous dital portion bent longitudinally at a 45º angle. 

G. noduliferum and G. lebak from slightly higher elevations of 170-800m have the chitinous dital portion bent at a 45º angle like the lowland species but is relatively less slender that the three species above. 

G. sukabumi and G. garutense from intermediate altitudes of 580-700m above sea level the G1 is relatively stouter and wider with the chitinous distal portion bent at a 70-80º angle along the longitudinal axis. 

The remaining highland species from elevations above 1000m sea level sow more variation but are always more robust and broad than lowland and intermediate species. G. robustum is relatively stout and bent at a 45º angle on the chitinous distal portion and G. confertum and G. cikaniki are relatively similar in shape but less bent. G. sekop the distal chitinous portion is bent at about a 30º angle with G. rouxi being bent at a 20º angle and the chitinous distal portion also relatively short. 

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