''Dardanus venosus'', the starry-eyed crab or stareye crab, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

hermit crab Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an a ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Diogenidae The Diogenidae are a family of hermit crabs, sometimes known as "left-handed hermit crabs" because in contrast to most other hermit crabs, its left chela (claw) is enlarged instead of the right. It comprises 429 extant species, and a further 46 e ...

. It occurs in shallow water on the eastern coasts of America from Florida southward to Brazil. It is sometimes kept in

reef aquaria A reef aquarium or reef tank is a marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the tropical coral reef environment. A reef aquarium requires appropriately ...

Description

''Dardanus venosus'' grows to a length of . As a hermit crab, it lives inside the empty shell of a

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

and its soft abdomen and most of its limbs are normally hidden with just the dactyls, or claws, projecting. Like other members of its family, it is left-handed, having its main

chela Chela may refer to: * ''Chela'' (fish), a genus of small minnow-type fish in the Cyprinid family * Chela (organ), a pincer-like organ terminating certain limbs of some arthropods such as crabs * Chela (meteorite), a meteorite fall of 1988 in Tan ...

or pincers on the left front limb. It uses this to cover the aperture of the shell when it feels threatened. The dactyls are a mauve colour due to the clusters of small bluish bristles that cover them. The crab's common name refers to the fact that when seen at close quarters, its eyes resemble star-bursts, being green or blue with dark pupils.

Distribution and habitat

''Dardanus venosus'' is found in Florida, the Caribbean Sea, the Gulf of Mexico, the Bahamas, the Antilles, Venezuela and Brazil from low tide mark down to about . It is found on various substrates including rock, gravel, sand, mud, shell, coral and seaweed.

Biology

''Dardanus venosus'' is a scavenger and consumes

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

and anything edible that it finds on the seabed. The life cycle of ''Dardanus venosus'' has been little studied but the eggs are probably brooded attached to the female's abdomen. When the eggs hatch, the larvae are liberated into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

and pass through several

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

l stages in the

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

before becoming glaucothoë larvae. These are relatively large and have elongated

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

s, or rear segments, and characteristic hooks on the dactyls of the walking legs. After some time, the glaucothoë larvae settle out before metamorphosing into juveniles that needs to find shells in which to live.

Ecology

In a study off the coast of Brazil, ''Dardanus venosus'' was found occupying eleven different kinds of gastropod shell including three different species of turban snail, ('' Astraea sp''). ''Dardanus venosus'' often has the

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

Calliactis tricolor ''Calliactis tricolor'', the tricolor anemone or hitchhiking anemone, is a species of sea anemone in the family Hormathiidae. It occurs in the Caribbean Sea and the Gulf of Mexico. It can be found attached to rocks but is often attached to a livi ...

'' attached to its shell. It actively collects the anemone off a rock or removes it from an outgrown shell when it moves into a larger one. It loosens the grip of the anemone by giving it several taps near the base, causing it to relax. At first the anemone clings to the new shell with its tentacles until its base has a firm grip on the shell. This is a mutualistic arrangement with both crab and anemone deriving benefit. The crab is protected by the stinging cells of the anemone and the anemone gains transport and a greater supply of food comes within its reach.

References

{{Taxonbar, from=Q3932173 Diogenidae Crustaceans described in 1848