Common name: Sea Cucumber Swimming Crab

Care

Caring for the Sea Cucumber Swimming Crab requires attention to its symbiotic relationship with sea cucumbers. It thrives in tanks that house compatible sea cucumber species, as it relies on them for shelter and food. A well-established reef tank with stable water parameters and plenty of live rock is ideal. These crabs are not demanding in terms of space, but their host sea cucumber's requirements should dictate the tank size and setup.

This species is relatively hardy but sensitive to sudden changes in water quality. Regular monitoring of salinity, temperature, and pH is essential to ensure its well-being. Providing a peaceful environment with minimal competition is crucial, as this crab is not aggressive and may be outcompeted by more dominant tank mates.

Diet and Feeding

The Sea Cucumber Swimming Crab is an opportunistic feeder, primarily consuming detritus, food scraps, and organic material found near its host sea cucumber. In captivity, it can be fed a diet of finely chopped seafood, frozen mysis shrimp, and high-quality pellets or flakes designed for omnivorous marine species. Ensuring that food reaches the crab can be challenging in larger tanks, so spot feeding may be necessary.

Feeding once or twice a day in small portions is sufficient. Overfeeding should be avoided to maintain water quality and prevent waste accumulation.

Behavior and Compatibility

This crab is peaceful and non-aggressive, making it an excellent choice for community reef tanks. Its symbiotic relationship with sea cucumbers is its most notable behavioral trait. The crab often positions itself on the body of its host, where it finds protection and food. It does not harm its host and can coexist with other peaceful tank inhabitants.

Avoid housing the Sea Cucumber Swimming Crab with aggressive or predatory species that may view it as prey. It is best kept in tanks with other small, non-aggressive invertebrates and fish.

Symbiosis

The Sea Cucumber Swimming Crab has a fascinating mutualistic relationship with sea cucumbers. It benefits from the protection provided by the sea cucumber's body and stinging cells, while the crab helps keep the sea cucumber clean by feeding on detritus and food particles around it. This relationship is a prime example of mutualism in marine ecosystems and can be replicated in captivity by pairing the crab with compatible sea cucumber species. Compatible sea cucumbers can be found in the genus Holothuria or in the genus Bohadschia, among others.

Health and Common Issues

This species is generally hardy but can be sensitive to poor water quality and sudden changes in tank conditions. Maintaining stable water parameters and a clean environment is essential for its health. When introducing the crab to a new tank, ensure that it has a compatible sea cucumber host and that the tank is free from aggressive species.

Common health issues include stress from incompatible tank mates or lack of a suitable host. Observing the crab's behavior and ensuring it remains active and well-fed can help prevent problems.

Habitat

Lissocarcinus orbicularis is naturally found in tropical Indo-Pacific waters, often in association with sea cucumbers. It inhabits shallow reef environments with sandy or rubble substrates, where it can easily find its host. Replicating these conditions in captivity, including providing a suitable sea cucumber host, is key to its success in a home aquarium.