Zaprionus tuberculatus

''Zaprionus tuberculatus'' (commonly known as the vinegar fly or the pomace fly) is a member of the subgenus and genus '' Zaprionus'', family Drosophilidae, and order Diptera. It is an invasive fruit fly that originated in Africa, but can also be found in Europe and Asia. The fly earned its common name, the "vinegar fly", because researchers frequently captured the species using vinegar traps. ''Z. tuberculatus'' was previously considered a strictly tropical fly, but evidence of invasion to nontropical regions such as Turkey has been shown.

This fly typically resides on rotting fruit, and the larvae have been found to develop on 49 species of fruits. The life cycle of the fly depends on the temperature of the environment as males are sterile at or above 30 degrees Celsius. It is reddish-brick colored and contains four longitudinal stripes down its head and body. The courtship behavior includes song singing and complex dance rituals. In regard to other organisms, ''Z. tuberculatus'' is considered a secondary pest to fruit and a potential threat to ecosystems it invades. A close relative, ''Z. indianus'' is an invasive fly species that infests fig orchards.

Taxonomy

''Zaprionus tuberculatus'' was first discriminated from its close relative ''Z. sepsoides'' in the 1970s.Tsacas L, David J, Allemand R, Pasteur G, Chassagnard MT, Derridj S.(1977) Biologie évolutive du genre Zaprionus. Recherches sur le complexe spécifique de Z. tuberculatus (Dipt. Drosophilidae). Annales de la Société entomologique de France 13: 391-415 ''Z. tuberculatus'' has recently classified as a member of the ''Tuberculatus'' species subgroup and is a member of the ''inermis'' species group. Previously, ''Z. tuberculatus'' was classified as a member of the armatus group. The genus ''Zaprionus'' if primarily found throughout Africa and contains 59 species, the most common of which being ''Z. indianus'' and ''Z. tuberculatus''.Patlar, B., Koc, B., Yilmaz, M. and Ozsov, E. D. 2012. First records of Zaprionus tuberculatus (Diptera: Drosophilidae) from the Mediterranean Region, Turkey. Drosophila Information Service 95: 94–96. The 59 species of the genus ''Zaprionus'' are divided into two subgroups: Afrotropical ''Zaprionus'' sensu stricto (s.s.), to which ''Z. tuberculatus'' belongs, and ''Anaprionus'' near Asia and Australia. Within the Zaprionus sensu stricto (s.s.) subgenus are several further subgroups, including the ''armatus'' subgroup to which ''Z. tuberculatus'' belonged until 2010.

Description

''Zaprionus tuberculatus'' contains four white horizontal stripes across its head and thorax, similar to other members of the ''Zaprionus'' subgroup. The males bear hairs on its forelegs. Both male and female flies have a protruding bristle from the forefemur. The frons have a medium-white stripe and the aedeagus is robust and curved and they have a dark-brown colored thorax. Two white, aligned, horizontal lines characterize the mesonotum and metanotum. ''Z. tuberculatus'' shares several common features with other members of the genus ''Zaprionus'', including a completely smooth larval cephalopharyngeal.

Reproductive system

Between individual flies, siblings are distinguished by testicular size (TST), for which the mean is 3.2mm. The average seminal recepaical (SR) of a female fly is 3.6mm.

Distribution

''Zaprionus tuberculatus'', originally from islands near the Indian Ocean and Afrotropical Region, then became invasive and expanded geographically to southern Europe. Within the Afrotropical region, the species has been reported in Mauritius, Réunion, Madagascar, Saint-Helena, Cape Verde, and Seychelles . The species had first been reported in Europe in Italy September, 2013. ''Z. tuberculatus'' has also been reported in North Africa, Malta, Cyprus, and the Canary Islands. ''Z. tuberculatus'' was trapped in Eastern Europe in Southern Romania between September and October 2014. ''Z. tuberculatus'' has been reported in a few other areas of Europe, including Spain, Greece, and Northern Italy. ''Z. tuberculatus'' has also been reported in Asian regions, including Israel and southern Turkey.

Habitat

''Zaprionus tuberculatus'' typically reside on rotting fruit and has been captured via the use of vinegar traps, which earned the species its nickname "vinegar fly." The fly does not thrive in strictly tropical environments.

Ecology

''Zaprionus tuberculatus'' is an invasive species, meaning its spread from one geographical region to other may harm to existing ecosystems.

Life cycle

''Zaprionus tuberculatus'' life cycle varies depending on the temperature of the environment. ''Zaprionus'' t''uberculatus'' males are sterile at or above 30 degrees Celsius. The mean ''Z. tuberculatus'' female life span varies from about 40 days to 60 days, whereas the mean male lifespan varies from about 50 to 200 days when temperature is varied.

Egg

The eggs of ''Z. tuberculatus'' have four filaments, with the posterior filaments being elongated more than the anterior filaments and are spatulated. The lengths of these filaments vary within species.

Larvae

The larvae of ''Z. tuberculatus'' generally grows on over-ripe fruits and has been found to develop on 49 species of fruits. Similar to other drosophilids, the larvae of ''Z. tuberculatus'' have a respiratory system containing thoracic and anterior spiracles on either side of the body, which is a systems organization referred to as amphipneustic.

Puparium

The pupae of ''Z. tuberculatus'' have a brick red color. The anterior branches belonging to ''Z. tuberculatus'' are clubbed type and vary in number from 11 to 14. The puparial shape (Puparial length:PI) of ''Z. tuberculatus'' is 2.59. Puparial shape is an important measurement because it distinguishes ''Z. tuberculatus'' from several closely related fly species, including ''Z. inermis'' (puparial shape =2.62), ''Z. cercus'' (puparial shape =2.40), and ''Z. burlai'' (puparial shape = 2.29). Similarly, another taxonomic measurement, the horn index (H) discriminates ''Z. tuberculatus'' (H= 7.0) from closely related fly species such as ''Z. verruca'' (H=10.6) and ''Z. burlai'' (H = 7.2). Unlike other species of ''Drosophila'' such as ''D. melanogaster'', for ''Z. tuberculatus'' pupae synapsis is uncommon and tend to pupariate upwards relate to the ground instead of downwards. However, ''Z. tuberculatus'' pupae strongly aggregate similar to other ''Drosophila'' species.

Behavior

Laboratory behavior

''Zaprionus tuberculatus'' pupae are difficult to study experimentally because, when space in culture bottles become limited, pupae climb upwards to escape from the bottle and later die. This is true for all species of the genus ''Zaprionus'', except ''Zaprionus lachaisei''.

Pupation site selection

Though kin selection theory predicts ''Z. tuberculatus'' pupae should be more likely to aggregate in an intraspecific manner than interspecifically, ''Z. tuberculatus'' does not kin discriminate in site selection.

Species recognition

"Type 2" songs are sung between two male ''Z. tuberculatus'' flies and its function is species recognition.

Mating

Male courtship behavior

The male ''Z. tuberculatus'' generally makes the first contact with the female ''Z. tuberculatus'' by grappling at the female, performing mating displays, then auditory display (song singing). The male performs stationary displays from the female ''Z. tuberculatus'' rear end at degrees of 90, 180, or 135 along the long axis of the female body. Still while singing, the male ''Z. tuberculatus'' then moves radially around the female in a quarter circle. From a further distance from the female compared to the circling display, the male ''Z. tuberculatus'' also performs a dancing which interrupts periods of singing or occurs after singing, but never before. Immediately preceding copulation, then for a second time at the beginning of copulation the male ''Z. tuberculatus'' also rubs his legs against the abdomen of the female ''Z. tuberculatus''. The average length of ''Z. tuberculatus'' copulation is about 2.25 minutes.

Male songs

Male ''Z. tuberculatus'' produces two types of songs by vibrating its wings to generate audio. The two song types are designated either "type 1," which is involved in male courtship, or "type 2," which is used for species recognition both in male and female ''Z. tuberculatus'' flies. When one male mounts another, both males sing, possibly to recognize sex or intimidation tactic to deter other males from attempting to mate with the female ''Z. tuberculatus'' flies.

Female courtship behavior

At the conclusion of copulation, female ''Z. tuberculatus'' protrudes the abdomen and secreted a colorless liquid, which appears to repulse the male ''Z. tuberculatus''. The chemical composition of the colorless liquid has not been studied.

Genetics

The ''Z. tuberculatus'' genome has five rod-shaped chromosomes and one dot-shaped chromosome. The number of type of chromosomes, or the karyotype, for ''Z. tuberculatus'' has not changed much throughout evolution, which supports Muller's linkage conservation hypothesis and explains the scarcity of pericentric inversions and translocations.

The transposable element ''mariner'' occurs in several species, including the ''Melanogaster'' species and in the genus ''Zaprionus''.Maruyama, Kyoko."Interspecific Transfer of the Transposable Element Mariner Between Drosophila and Zaprionus," (PhD diss., Washington University in St.Louis School of Medicine,1991). The presence of ''mariner'' in the ''Z. tuberculatus'' occurs through horizontal transfer. ''Mariner'' is also present in several members of the ''melanogaster'' species subgroup. The rate of divergence of the ''mariner'' element between the two species subgroups suggests a slower evolution rate of the ''mariner'' transposable element. A slowing ''mariner'' mutation rate helps to explain low divergence in the ''melanogaster'' species subgroup, but fails to account for reduced divergence in Z. tuberculatus. The specific mechanism by which horizontal transfer of mariner occurs for ''Z.tuberculatus'' is currently unknown and is being investigated. Similarly, study of the retrosposon ''copia'' also revealed evidence supporting horizontal transfer between ''Z. tuberculatus'' and the ''melanogaster'' species subgroup.

Interactions with humans

''Zaprionus tuberculatus'' is a pest in regions to which it has invaded and infects fruit. ''Z. tuberculatus'' is thus capable of negatively impacting fruit which humans eat, but it is unknown which fruit species are most negatively influenced. A close relative of ''Z''. ''tuberculatus'', ''Z. indianus'', is an invasive fly species and a pest to fig orchards. However, the adverse ecological influences of ''Z. tuberculatus'' has only recently been investigated directly.Leivadaras J, Leivadara EI, Vontas J (2017) A new insect, drosophila ''Zaprionus tuberculatus'' (Diptera: Drosophilidae), affects the figs on Crete. Abstract of a paper presented at the Panhellenic Entomological Congress (Athens, GR, 2017-09-19/22), p 27.

References

{{Taxonbar, from=Q13851763

Drosophilidae
Insects described in 1932