Sepsis thoracica

Last updated

Sepsis thoracica
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Sepsidae
Subfamily: Sepsinae
Genus: Sepsis
Species:
S. thoracica
Binomial name
Sepsis thoracica
Synonyms
  • Micropeza thoracica Robineau-Desvoidy, 1830
  • Sepsis tridens Becker, 1903
  • Sepsis propinquusAdams, 1905
  • Sepsis modesta Meijere, 1906
  • Sepsis consanguinea Villeneuve, 1920
  • Sepsis goetghebueri Frey, 1925
  • Sepsis quadratipunctata Brunetti, 1929
  • Sepsis longisetosa Brunetti, 1929
  • Sepsis idmais Séguy, 1932
  • Sepsis ino Séguy, 932:
  • Sepsis inermis Séguy, 1933
  • Sepsis longisetaVanschuytbroeck, 1961
  • Sepsis quadripunctataVanschuytbroeck, 1961
  • Sepsis kamahoroensisVanschuytbroeck, 1963

Sepsis thoracica, more commonly known as the black scavenger fly, a species of fly from the genus Sepsis and the family Sepsidae. It was discovered by Robineau-Desvoidy in 1830. It resembles a small flying ant. The fly is most commonly found inhabiting cow dung.

Contents

Sepsis thoracica shows positive directional selection in body size that corresponds with negative selection of melanism. In addition, body size and coloration are coupled via gene regulation. A hypothesized mechanism is through the enzyme phenoloxidase.

Description

Sepsis thoracica is a relatively small fly (often described as ant-like), averaging 5 mm in length and 0.75 mm in width. [2] They have a rounded head with compound eyes. The last segment of the body contains short, silver hair. Their wings are mostly transparent with dark spots towards the ends. The developmental temperature influences their body size, in accordance with the temperature-size rule. [3] Females are completely black and smaller than males.

Male polymorphism

Males can be either black or amber, a coloration that is usually only observed in more tropical species. S. thoracica is the only fly of the genus Sepsis to exhibit this male polymorphism in relation to size. While males can be a spectrum of colors between black and amber, most are usually one of the extremes. [3] [4]

Thermal radiation, which is the long-waves emitted by the atmosphere, is important in the development of S. thoracica because the

Distribution

Sepsis thoracica has a wide distribution. It is mainly found in Europe, particularly in the United Kingdom, extending as far north as Denmark and southern Sweden. It is also in Afrotropical and Australasian regions. It has most recently been found in Vietnam and South Korea. It is mostly dispersed near the coasts and at high elevations in mountain ranges. [5]

Habitat

Cow Dung Cow dung 34.jpg
Cow Dung

Sepsis thoracica is a dung fly and prefers cow dung and buffalo dung, especially in human-managed agricultural grasslands. [6] However, the flies typically avoid horse dung. [7] They are a tropical and subtropical species that are extremely heliophilic, or attracted to sun. [8] They are most active between the months of July and October.

Life history

Females deposit their eggs into the dung. [6] The larvae are not able to escape this during development and thus the flies only leave when they are adults. The larvae are amphipneustic, meaning that both their first and last spiracles are functional. The two spiracle pairs of the respiratory system are on the prothorax and the posterior of the abdomen. [2] The developmental time of the larvae is four days and five hours, optimally at a temperature of 26-28 °C. In cow dung, 15–22 days marks the total developmental time. These flies enter dormancy in response to dropping temperatures. [5]

Food resources

Sc. stercoraria Yellow Dung Fly (Scathophaga stercoraria) - Kitchener, Ontario 02.jpg
Sc. stercoraria

They spend a considerable amount of their life foraging for nectar and their insect prey, Sc. stercoraria . They feed on dung for protein and nectar for carbohydrates. While they are found to mostly feed on cow dung, they have been shown to feed on horse dung if it is available in their area. [9] The competitor density they face largely depends on the amount of eggs laid in the dung pat from which they emerged. [5] They don’t face much outside species competition.

Mating

Sexual selection

Sepsis thoracica has shown a strong, positive directional selection on body size that coincides with a strong negative selection of melanism. The dichotomous coloration is thought to have evolved as a way to indicate their size and fitness. [9] The purity of amber color relating to size was most likely maintained due to the cost it retains from reduced immunity. This causes a trait threshold, where only the largest individuals in a competitive environment can afford to be amber. The larger, amber-colored males are favored by females over the small, black males. However, black males have greater success than mid-sized, mid-toned males. [4] [9] Mating practices do not differ between males of different colors, but reproductive fitness is higher in the larger, amber males,

Copulation

Sepsis thoracica does not exhibit any pre or post-copulatory guarding in Europe, but it does have pre-copulatory guarding in more tropical areas, such as Zimbabwe. [10] This mating behavior occurred on the dung pat, with males scrambling and competing for the exceedingly rare single females. Male rejection and struggle behavior does occur. When a mate is found, copulations take place in the nearby vegetation. S. thoracica has relatively long copulation and guarding durations, similar to S. cynipsea. [10]

Enemies

Sepsis thoracica faces mostly generalist predators in their pastoral habitat. [9] Vertebrates include birds, Lacerta lizards, and amphibians when close enough to ponds. The main predators are terrestrial invertebrates, like spiders and insects, primarily other flies and wasps. When dealing with vertebrate predators, black S. thoracica have a greater advantage over amber-colored flies. When encountering an invertebrate predator, being larger is more advantageous than being black. Since S. thoracica is most likely to encounter an invertebrate predator, size is the best defense mechanism for S. thoracica.

Genetics

Body size and coloration are coupled together, likely via gene regulation. They have been shown to be functionally linked through the enzyme phenoloxidase, which works in the phenoloxidase system. [3] [11] This system is the main immunological defense system of S. thoracica. The reduction in melanin conforms with lower amounts of phenoloxidase, which compromises the immune system. This causes larger, amber individuals to be immunocompromised. [11] This polymorphism is seen in related species such as Saltella sphondylii, implying a more general evolutionary relevance. [3]

Physiology

Thermal radiation

Thermal radiation, which is the long-waves emitted by the atmosphere, is important in the development of S. thoracica because the dung on which the flies eat absorbs most of the short-wave radiation from the sun because of its dark color. This causes the dung to emit long-wave radiation which is absorbed by the flies. The amount of long-wave absorbance does not differ based on the amount of melanism because it’s out of melanin’s spectrum; consequently, absorption relies only on size. Larger individuals thus absorb the most radiation but also have a lower heat-exchange rate with the environment due to its low surface volume ratio. Larger flies retain more heat and are more prone to overheating. This can be compensated by lower melanism, which absorbs the short-wave radiation. The reduction in short-wave radiation can negate the effects of the long-wave radiation, allowing both amber and black colored S. thoracica to have relatively similar temperatures. [3]

UV radiation

Protection from UV radiation is also exploited by the dichotomous nature of the males. Black flies have a high amount of melanin, which they use to directly protect itself from UV damage. Amber flies invest in their cuticle, which becomes thicker with increased size. [3] Thus, beyond a threshold, UV radiation will have little to no penetrance. This is an importance defense mechanism since UV radiation can lead to unwanted genetic mutations.

Related Research Articles

<span class="mw-page-title-main">Melanin</span> Group of natural pigments found in most organisms

Melanin is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes. Functionally, eumelanin serves as protection against UV radiation.

<span class="mw-page-title-main">Piophilidae</span> Family of flies

The Piophilidae are a family of "true flies", in the order Diptera. The so-called cheese flies are the best-known members, but most species of the Piophilidae are scavengers in animal products, carrion, and fungi. They may accordingly be important in forensic entomology and medical entomology. For a fly maggot, the larvae of many species have an unusually well-developed ability to leap when alarmed or when abandoning their larval food to pupate; they accordingly may be known as cheese skippers or other kinds of skippers according to their food source.

<span class="mw-page-title-main">Fly</span> Order of insects

Flies are insects of the order Diptera, the name being derived from the Greek δι- di- "two", and πτερόν pteron "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced mechanosensory organs known as halteres, which act as high-speed sensors of rotational movement and allow dipterans to perform advanced aerobatics. Diptera is a large order containing an estimated 1,000,000 species including horse-flies, crane flies, hoverflies and others, although only about 125,000 species have been described.

<span class="mw-page-title-main">Sepsidae</span> Family of flies

The Sepsidae are a family of flies, commonly called the black scavenger flies or ensign flies. Over 300 species are described worldwide. They are usually found around dung or decaying plant and animal material. Many species resemble ants, having a "waist" and glossy black body. Many Sepsidae have a curious wing-waving habit made more apparent by dark patches at the wing end.

<span class="mw-page-title-main">Melanism</span> Increased development of melanin in the skin or hair

The term melanism refers to black pigment and is derived from the Greek: μελανός. Melanism is the increased development of the dark-colored pigment melanin in the skin or hair.

<span class="mw-page-title-main">Phoridae</span> Family of flies

The Phoridae are a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behaviour is a source of one of their alternate names, scuttle fly. Another vernacular name, coffin fly, refers to Conicera tibialis. About 4,000 species are known in 230 genera. The most well-known species is cosmopolitan Megaselia scalaris. At 0.4 mm in length, the world's smallest fly is the phorid Euryplatea nanaknihali.

<span class="mw-page-title-main">Stalk-eyed fly</span> Family of dipteran insects with antennae located on eyestalks

Stalk-eyed flies are insects of the fly family Diopsidae. The family is distinguished from most other flies by most members of the family possessing "eyestalks": projections from the sides of the head with the eyes at the end. Some fly species from other families such as Drosophilidae, Platystomatidae, Richardiidae, and Tephritidae have similar heads, but the unique character of the Diopsidae is that their antennae are located on the stalk, rather than in the middle of the head as in all other flies. Stalked eyes are present in all members of the subfamily Diopsinae, but are absent in the Centrioncinae, which retain unstalked eyes similar to those of other flies. The stalked eyes are usually sexually dimorphic, with eyestalks present but shorter in females.

<span class="mw-page-title-main">Nematocera</span> Suborder of flies

The Nematocera are a suborder of elongated flies with thin, segmented antennae and mostly aquatic larvae. This group is paraphyletic and contains all flies but species from suborder Brachycera, which includes more commonly known species as housefly or the common fruit fly. Families in Nematocera include mosquitoes, crane flies, gnats, black flies, and a multiple groups of families described as midges. The Nematocera typically have fairly long, fine, finely-jointed antennae. In many species, such as most mosquitoes, the female antennae are more or less threadlike, but the males have spectacularly plumose antennae.

<span class="mw-page-title-main">Carnoidea</span> Superfamily of flies

Carnoidea is a superfamily of Acalyptratae flies.

<span class="mw-page-title-main">Scathophagidae</span> Family of flies

The Scathophagidae are a small family of Muscoidea which are often known as dung flies, although this name is not appropriate except for a few species of the genus Scathophaga which do indeed pass their larval stages in animal dung. The name probably derives from the yellow dung fly, which is one of the most abundant and ubiquitous flies in many parts of the Northern Hemisphere.

<i>Eristalis tenax</i> Species of fly

Eristalis tenax, the common drone fly, is a common, migratory, cosmopolitan species of hover fly. It is the most widely distributed syrphid species in the world, and is known from all regions except the Antarctic. It has been introduced into North America and is widely established. It can be found in gardens and fields in Europe and Australia. It has also been found in the Himalayas.

<span class="mw-page-title-main">Biological pigment</span> Substances produced by living organisms

Biological pigments, also known simply as pigments or biochromes, are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biological structures, such as skin, eyes, feathers, fur and hair contain pigments such as melanin in specialized cells called chromatophores. In some species, pigments accrue over very long periods during an individual's lifespan.

<span class="mw-page-title-main">Flower mantis</span> Species of mantis camouflaged to resemble flowers to lure their prey

Flower mantises are praying mantis species that use a special form of camouflage referred to as aggressive mimicry, which they not only use to attract prey, but avoid predators as well. These insects have specific colorations and behaviors that mimic flowers in their surrounding habitats. This strategy has been observed in other mantises including the stick mantis and dead-leaf mantis. The observed behavior of these mantises includes positioning themselves on a plant and either inserting themselves within the irradiance or on the foliage of the plants until a prey insect comes within range. Many species of flower mantises are popular as pets. The flower mantises are non-nocturnal group with a single ancestry, but the majority of the known species belong to family Hymenopodidea.

<span class="mw-page-title-main">Animal coloration</span> General appearance of an animal

Animal coloration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are brightly coloured, while others are hard to see. In some species, such as the peafowl, the male has strong patterns, conspicuous colours and is iridescent, while the female is far less visible.

<i>Scathophaga stercoraria</i> Species of fly

Scathophaga stercoraria, commonly known as the yellow dung fly or the golden dung fly, is one of the most familiar and abundant flies in many parts of the Northern Hemisphere. As its common name suggests, it is often found on the feces of large mammals, such as horses, cattle, sheep, deer, and wild boar, where it goes to breed. The distribution of S. stercoraria is likely influenced by human agriculture, especially in northern Europe and North America. The Scathophaga are integral in the animal kingdom due to their role in the natural decomposition of dung in fields. They are also very important in the scientific world due to their short life cycles and susceptibility to experimental manipulations; thus, they have contributed significant knowledge about animal behavior.

<span class="mw-page-title-main">Eristalinae</span> Subfamily of flies

Eristalinae are one of the four subfamilies of the fly family Syrphidae, or hoverflies. A well-known species included in this subfamily is the dronefly, Eristalis tenax.

<i>Arctia plantaginis</i> Species of moth

Arctia plantaginis, the wood tiger, is a moth of the family Erebidae. Several subspecies are found in the Holarctic ecozone south to Anatolia, Transcaucasus, northern Iran, Kazakhstan, Mongolia, China, Korea and Japan. One subspecies is endemic to North America.

<i>Sepsis cynipsea</i> Species of fly

Sepsis cynipsea is a European species of fly and member of the family Sepsidae. It is a coprophagous fly that feeds on dung. These flies are most commonly found around freshly laid cattle dung where they eat and reproduce. Due to human agricultural practices involving cows, these flies are now common in other areas of the world.

Diptera is an order of winged insects commonly known as flies. Diptera, which are one of the most successful groups of organisms on Earth, are very diverse biologically. None are truly marine but they occupy virtually every terrestrial niche. Many have co-evolved in association with plants and animals. The Diptera are a very significant group in the decomposition and degeneration of plant and animal matter, are instrumental in the breakdown and release of nutrients back into the soil, and whose larvae supplement the diet of higher agrarian organisms. They are also an important component in food chains.

<i>Prolepsis</i> (fly) Genus of flies

Prolepsis is an insect genus of mainly neotropical Diptera in the family Asilidae or robber flies.

References

  1. Robineau-Desvoidy, André Jean Baptiste (1830). "Essai sur les myodaires". Mémoires presentés à l'Institut des Sciences, Lettres et Arts, par divers savants et lus dans ses assemblées: Sciences, Mathématiques et Physique. 2 (2): 1–813. Retrieved 15 July 2018.
  2. 1 2 Meier, Rudolf (January 1996). "Larval morphology of the Sepsidae (Diptera: Sciomyzoidea), with a cladistic analysis using adult and larval characters". Bulletin of the American Museum of Natural History. 228: 3–147.
  3. 1 2 3 4 5 6 Busso, Juan Pablo; Blanckenhorn, Wolf U. (March 2018). "Climatic factors shape plastic trade-offs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae)" (PDF). Journal of Biogeography. 45 (3): 593–603. doi:10.1111/jbi.13140. ISSN   1365-2699. S2CID   90754107.
  4. 1 2 Busso, Juan Pablo; Blanckenhorn, Wolf U. (2018-05-09). "Disruptive sexual selection on male body size in the polyphenic black scavenger fly Sepsis thoracica". Behavioral Ecology. 29 (3): 769–777. doi:10.1093/beheco/ary038. ISSN   1045-2249.
  5. 1 2 3 Zeender, Valérian; Roy, Jeannine; Wegmann, Alexandra; Schäfer, Martin A.; Gourgoulianni, Natalia; Blanckenhorn, Wolf U.; Rohner, Patrick T. (April 2019). "Comparative reproductive dormancy differentiation in European black scavenger flies (Diptera: Sepsidae)". Oecologia. 189 (4): 905–917. Bibcode:2019Oecol.189..905Z. doi:10.1007/s00442-019-04378-0. ISSN   1432-1939. PMID   30877577. S2CID   253982071.
  6. 1 2 Bai, M. Geetha; Sankaran, T. (1977-06-01). "Parasites, predators and other arthropods associated with Musca domestica and other flies breeding in bovine manure". Entomophaga. 22 (2): 163–167. doi:10.1007/BF02377838. ISSN   1573-8248. S2CID   24834670.
  7. Hafez, M. (1948). "Ecological and Biological Observations on Somi3 Copro-Phagous Sepsidae (diptera)". Proceedings of the Royal Entomological Society of London, Series A. 23 (10–12): 99–104. doi:10.1111/j.1365-3032.1948.tb00608.x. ISSN   1365-3032.
  8. Pont, Adrian (1987). Provisional Atlas of the Sepsidae (Diptera) of the British Isles (PDF). British Records Centre. ISBN   1-870393-00-7 . Retrieved 2019-10-31.
  9. 1 2 3 4 Busso, Juan Pablo; Blanckenhorn, Wolf U. (July–August 2018). "Viability selection by invertebrate predators in the polyphenic black scavenger fly Sepsis thoracica". Behavioral Ecology. 29 (4): 992–1000. doi: 10.1093/beheco/ary039 .
  10. 1 2 Blanckenhorn, Wolf U.; Cozzi, Gabriele; Jäggli, Gregory; Busso, Juan Pablo (2019-05-08). "Size- and sex-specific predation on dung flies by amphibian and arthropod predators – size match matters". bioRxiv: 631549. doi: 10.1101/631549 .
  11. 1 2 Busso, Juan P.; Blanckenhorn, Wolf U.; González‐Tokman, Daniel (2017). "Healthier or bigger? Trade-off mediating male dimorphism in the black scavenger fly Sepsis thoracica (Diptera: Sepsidae)" (PDF). Ecological Entomology. 42 (4): 517–525. doi:10.1111/een.12413. ISSN   1365-2311. S2CID   90767249.