''Drosophila endobranchia'' 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 ...

fly Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...

in the family Drosophilidae. The species, which is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to Grand Cayman, was discovered in 1966 and not found again until 2007, when it was rediscovered in the mouth region of a

land crab A number of lineages of crabs have evolved to live predominantly on land. Examples of terrestrial crabs are found in the families Gecarcinidae and Gecarcinucidae, as well as in selected genera from other families, such as ''Sesarma'', althou ...

Habitat

Like most drosophilid flies, ''D. endobranchia'' feeds on

microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s. Peculiarly, this and two other species have colonized

s. While the Christmas Island fly '' Lissocephala powelli'' lives on both true crabs and Anomura (for example ''

Birgus latro The coconut crab (''Birgus latro'') is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest terrestrial arthropod in the world, with a weight of up to . It can grow to up to in width from the tip ...

'', the robber crab), ''D. endobranchia'' and the closely related '' D. carcinophila'' live on gecarcinid crabs such as the black ''

Gecarcinus ruricola ''Gecarcinus ruricola'' is a species of terrestrial crab. It is the most terrestrial of the Caribbean land crabs, and is found from western Cuba across the Antilles as far east as Barbados. Common names for ''G. ruricola'' include the purple land ...

'' and the red '' G. lateralis''. ''D. endobranchia'' prefers ''G. ruricola''. One reason could be that ''G. lateralis'' digs its own burrows, which could lead to problems for the flies living on its surface.

Biology

''D. endobranchia'' is closely associated with its crab host, with one to six flies found per infected crab. Adults hardly move at all, let alone fly, and are extremely reluctant to leave their fast-paced host. Courting and mating take place on the crab, and territories are defended between males. The eggs are placed around the crab's eyes. The hatched

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e migrate to the nephric pads and feed on microbes responsible for cleansing

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

from

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

ous compounds. From the second

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

on, the larvae migrate to the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

chamber, where they stay up to several months. At the third instar they return to the mouth parts where they form a halo around the mouth opening. They later fall to the ground to

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

te. At least three quarters of adult ''D. endobranchia'' found on land crabs were males. It is not clear whether this species has a skewed sex ratio, or whether females only visit crabs, or frequently switch host crabs. Host crabs are found using olfactory cues, but the substance or substances responsible for this are not known.

Conservation

Habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and hunting pose a threat to the long-term survival of black crabs on Grand Cayman, and thus also to their fly guests. It has therefore been proposed to classify host and guest as vulnerable.

Habitat

Biology

Conservation

References

Further reading