The blue-spotted hermit crab (Dardanus guttatus), belongs to the Decapoda order, and within this to the Diogenidae family. This species of crab inhabits the waters of the western Indo-Pacific, from the coasts of East Africa to southern China and also the Hawaiian Islands. It has a preference for coral bottoms or rocky substrates within the lagoons and coral bays. As for the range of depths in which we can find this species, this will be from the shallowest waters to approximately 50 meters deep.
The body of Dardanus guttatus is very flat and dark red in color, with numerous small white spots distributed throughout the body. The distinguishing feature that makes identification of this species relatively simple is the presence of an intense blue disc on the joints of each of its legs, as well as on the thorax, although the latter spots are not always visible as they are generally covered by the shell in which they live. All appendages of this species are covered with numerous hairs.
As with all hermit crabs do, Dardanus guttatus uses mollusc shells in which to insert the abdomen of its body and thus gain protection from predators. The shell preference of this species is for those with narrow openings, such as those of cone snails. As the individual grows, it changes to a shell according to its size, allways looking for a better one to their needs.
The diet of Dardanus guttatus is predominantly carnivorous, actively preying on different species of snails, clams and small fish, although occasionally it also feeds on small invertebrates or even some filamentous algae. Unlike most hermit crabs that are usually active at night to avoid predatory fish, in the case of Dardanus guttatus it is both active at night and during the day.Photos: