Invertebrate atlas

Geographical Origin and Habitat: Widely distributed in Polynesia, Melanesia, Indonesia, and various islands of the Indian and Pacific Oceans. Inhabits rainforest undergrowth and shaded beach areas. They require access to both coastal dunes and dense vegetation zones to complete their life cycles. They are often found deep in the forest litter during the day.

Taxonomy: Member of the family Coenobitidae. Characterized by sharp, dark tubercles and spine-like nodules covering its walking legs and claws. Grows to about 8-10 cm. The species name spinosus highlights the prominent protective spines on their exoskeleton. They are closely related to other Indo-Pacific land hermit crabs.

Social Behavior: Peaceful and gregarious, but tends to be more reclusive than other species. Prefers the damp leaf litter of inland forests over open sandy beaches. Active primarily at night. They communicate through soft stridulation sounds produced by rubbing their limbs together. This behavior is more pronounced during feeding times.

Coloration and Sexual Dimorphism: Body color is typically dark: dark brown, smoky grey, almost black, or deep brick red. The spines on the legs are black or very dark. No visible external sexual dimorphism. Their heavy exoskeleton requires a continuous supply of calcium to maintain its structural integrity. The coloration darkens significantly after each successful molt.

Tank Setup: Requires a dry terrarium with at least 6-8 inches of substrate made of fine sand and coconut fiber. The substrate must remain moist to support burrowing and molting. Provide branches and bark. The substrate depth should be at least three times the height of the largest crab. Use a mix of play sand and organic coco peat.

Diet and Feeding: Opportunistic omnivore. Eats dried leaves, fresh fruits, vegetables, dried insects, fish meat, and specialized pellets. Cuttlebone must be supplied to provide calcium. Incorporate foods high in beta-carotenes, like carrots and squash, to maintain vibrant color after molting. Offer small amounts of animal protein regularly.

Water Quality: Provide two shallow water dishes: one with dechlorinated fresh water, and one with marine salt water. Keep relative humidity at 70-80% to maintain moist gills. Always use a high-quality aquarium dechlorinator for all water sources. Saltwater pools must have a salinity comparable to natural seawater.

Compatibility and Tankmates: Keep only in terrariums with other land hermit crab species. Coexists peacefully in large groups of its own or related species (Coenobita). Provide at least 3 to 5 extra empty shells per crab to prevent shell fights. Ensure the shells are clean and have smooth openings.

Aquarium Breeding: Larval development involves a marine zoeal phase that requires open ocean conditions and specialized planktonic foods to survive. Successful captive breeding has only been achieved in highly controlled scientific laboratories. The zoea stages are highly sensitive to water currents.

Risks and Diseases: Fast dehydration and death if humidity drops below 70%. Risk of mold infections if substrate is waterlogged. Molting failure if substrate is too dry or shallow. Ensure the molting area is not disturbed by other crabs, as newly molted crabs are very soft. Avoid digging up a buried crab unless it is an emergency.