Chameleon land crab

Geographical Origin and Habitat: Metasesarma aubryi is widely distributed across the tropical regions of the Indo-Pacific, including the islands of Indonesia, Papua New Guinea, the Philippines, and various South Pacific islands. It inhabits humid terrestrial environments near freshwater streams, coastal rainforests, and damp lowland forests, often venturing further inland than other land crabs. It is commonly found under moist leaf litter, inside rotting logs, or climbing low vegetation.

Taxonomy: This species belongs to the class Malacostraca, order Decapoda, family Sesarmidae, and genus Metasesarma. It is commonly known as the chameleon land crab or Aubry's land crab due to its variable color patterns and adaptation to terrestrial life. No commercial color breeds exist, and individuals in the pet trade preserve their wild genetic traits.

Social Behavior: It is primarily nocturnal and crepuscular, though it may show daytime activity under dense canopy shade and high humidity. It exhibits distinct semi-arboreal habits, climbing branches and cork bark. It is not overly aggressive toward conspecifics if provided with a large enclosure and plenty of hiding spots, though males will establish territories.

Coloration and Sexual Dimorphism: The coloration is highly variable, ranging from reddish-brown to bright orange, with claws that are often bright yellow or pale white. The carapace is smooth and bulbous. Sexual dimorphism is determined by inspecting the abdominal flap on the underside: males have a narrow, triangular flap, whereas females possess a wide, rounded flap used to carry and protect eggs.

Tank Setup: Requires a humid terrarium or a paludarium with a major terrestrial area (at least 80% land) and a shallow, easily accessible freshwater pool. The minimum enclosure size for a small group is 60x40x40 cm. The substrate should consist of moist coconut fiber, peat, or sphagnum moss, at least 5-8 cm deep to allow burrowing. Climbing structures such as branches, cork bark, and live plants must be provided.

Diet and Feeding: An opportunistic omnivore and detritivore. In captivity, feed a varied diet including fresh fruits (banana, apple), blanched vegetables (zucchini, carrots), dry fish or shrimp pellets, and animal proteins like dead insects, dried shrimp, or bloodworms. Powdered calcium carbonate or cuttlebone must be provided regularly to ensure successful molting of the exoskeleton.

Water Quality: The freshwater pool must contain dechlorinated water free of heavy metals. Water and air temperatures should be maintained between 24°C and 28°C. The water must be changed frequently or filtered with a gentle low-profile internal filter, as these crabs tend to drag organic matter into the pool, which quickly spoils the water.

Compatibility and Tankmates: Best kept in small groups consisting of one male and multiple females. Avoid housing multiple males in confined spaces to prevent fighting. Do not keep with small fish or amphibians that they could pinch, nor with large predators. They can cohabit peacefully with clean-up crew organisms like isopods, springtails, and land snails.

Aquarium Breeding: Breeding in home terrariums is extremely difficult and rarely successful. While the female carries fertilized eggs under her abdomen, the hatching larvae (zoea stage) require a brackish or marine water environment to develop. Transitioning the post-larval crabs from saltwater back to a terrestrial setup is a complex task requiring scientific protocols.

Risks and Diseases: Dehydration is the greatest threat to this species; ambient humidity must be kept high at 75-85% through daily misting. During the molting process, the crab is soft and vulnerable. It will hide and must never be handled or disturbed, as a failed molt is fatal or can cause permanent limb loss.