This time we will be introducing a crab of the genus Geosesarma that lives in freshwater areas of Indonesia.
Previously, this family was placed in the Grapsidae family, but now it is placed in the Crassulinidae family (Sesarmidae). The family Crassulaceae is a group that includes the Japanese red crab, which is well-known as a pet in Japan. A common feature of this family is that the shape of the shell is more angular than that of the Japanese freshwater crab.
Although red-eared crabs, crabs, and black crabs sometimes expand their habitats from seawater to brackish water and even freshwater, the larvae that hatch from eggs generally grow in the sea. Most crabs belonging to this family are marine and small-ovoid. On the other hand, crabs of the genus Geothesarma have further adapted to living on land and have acquired a land-locked breeding style that ends their lives in freshwater areas. They lay slightly larger eggs, spend their larval stage inside the eggs, and hatch into baby crabs.

Some species, such as those living in Malaysia and Singapore, have evolved in even more unique directions. Their habitat is not the waterside, but the water inside the Nepenthes.
Although they are ecologically very interesting, what is noteworthy about crabs of this genus is their size. In most species, the carapace width does not exceed 2 cm. This is a very small variety of crabs.
This genus of crabs is widely distributed from the Philippines to Indonesia, Malaysia, and Thailand, and nearly 50 species have been described. Among them, several types from Indonesia have been constantly arriving in the past few years.
Representative species include Kalimantan Red Crab and Vampire Crab, but care must be taken as different species may arrive with the same invoice name.

The type introduced in the photo this time also came from Indonesia under the invoice name Red Carnival Club, but in Japan it is popularly known as Deep Red Vampire Club. There is no doubt that it belongs to the genus Geothesarma, but its scientific name is currently unknown. The individuals that arrived on the same flight are highly variable in color, with some having bright red shells, some with half red, some with slightly orange color, and some with mottled patterns. This type of color variation between individuals can also be seen in vampire clubs.

Since this species is small, it is not difficult to raise them. When breeding them, it is best to use small plastic cases or all-glass aquariums. I'll build a shallow water hole and make the land area wider. When I observe them, I find that they usually don't like being in the water and are more often found on land. Although it is possible to keep crabs with a simple layout of just gravel and driftwood, creating a mini terrarium with moss and miniature ornamental plants will look great, and the crabs will also have a place to hide and feel calm.
What you need to be careful about when breeding them is escape. Crabs of this genus have excellent athletic ability and are quite agile in their movements. For example, it runs around as fast as a cockroach. They also easily escape from the tank by climbing up air tubes. Therefore, be sure to cover the breeding container tightly so that there are no gaps.

They will eat anything, including artificial fish feed and frozen bloodworms, so feed them little by little so that there are no leftovers.
It is also easy to distinguish between males and females. Males have slightly larger pincers, while females do not. You can also tell by looking at the part of the abdomen commonly known as the crab's loincloth. Males are triangular and thin, and females are large and round. If you keep a male and a female, they can mate in the tank, lay eggs, and breed.
Crabs of the genus Geothesarma, which can be easily kept in small aquariums and are highly collectible, are likely to become more popular in the future. We want you to experience its charm as soon as possible.