Drosophila endobranchia is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of fly

Fly

True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

 in the family Drosophilidae

Drosophilidae

Drosophilidae is a diverse, cosmopolitan family of flies, which includes fruit flies. Another family of flies called Tephritidae also includes fruit flies. The best known species of Drosophilidae is Drosophila melanogaster, within the genus Drosophila, and this species Is used extensively for...

. The species, which is endemic to Grand Cayman

Grand Cayman

Grand Cayman is the largest of the three Cayman Islands and the location of the nation's capital, George Town. In relation to the other two Cayman Islands, it is approximately 75 miles southwest of Little Cayman and 90 miles southwest of Cayman Brac.-Geography:Grand Cayman encompasses 76% of...

, was discovered in 1966 and not found again until 2007, when it was rediscovered in the mouth region of a land crab

Land crab

Gecarcinidae is a family of true crabs that are adapted for terrestrial existence, commonly known as land crabs. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs...

.

Habitat

Like most drosophilid flies, D. endobranchia feeds on microbes. Peculiarly, this and two other species have colonized land crab

Land crab

Gecarcinidae is a family of true crabs that are adapted for terrestrial existence, commonly known as land crabs. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs...

s. While the Christmas Island

Christmas Island

The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located northwest of the Western Australian city of Perth, south of the Indonesian capital, Jakarta, and ENE of the Cocos Islands....

 fly Lissocephala powelli lives on both true crabs

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

 and Anomura

Anomura

Anomura is a group of decapod crustaceans, including hermit crabs and others. Although the names of many anomurans includes the word crab, all true crabs are in the sister group to the Anomura, the Brachyura .-Description:The name Anomala reflects the unusual variety of forms in this group;...

 (for example Birgus latro, the robber crab), D. endobranchia and the closely related D. carcinophila live on gecarcinid crabs such as the black Gecarcinus ruricola

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...

and the red G. lateralis

Gecarcinus lateralis

Gecarcinus lateralis, also known by the common names blackback land crab, Bermuda land crab, red land crab and moon crab Gecarcinus lateralis, also known by the common names blackback land crab, Bermuda land crab, red land crab (leading to easy confusion with Gecarcoidea natalis) and moon crab...

. 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

Larva

A larva 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...

e migrate to the nephric pads

Nephron

The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system, which is not part of the nephron....

 and feed on microbes responsible for cleansing urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 from nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

ous compounds. From the second instar

Instar

An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...

 on, the larvae migrate to the gill

Gill

A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

 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

Pupa

A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

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

Olfaction

Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...

, but the substance or substances responsible for this are not known.

Conservation

Habitat destruction 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.