User:Mer0814/Chironomidae

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Behavior and description
Chironomids as a group are very diverse in their life histories, and exhibit a variety of behaviors during their development. Due to their species ambiguity and this diversity of behaviors, there is much controversy in research on their feeding habits, particularly as adults.

Many reference sources in the past century or so have repeated the assertion that the Chironomidae do not feed as adults, but an increasing body of evidence contradicts this view. Adults of many species do, in fact, feed. The natural foods reported include fresh fly droppings, nectar, pollen, honeydew, and various sugar-rich materials.

TALK ABOUT EMERGENCE BEHAVIORS

The question whether feeding is of practical importance has by now been clearly settled for some Chironomus species, at least; specimens that had fed on sucrose flew far longer than starved specimens, and starved females longer than starved males, which suggested they had eclosed with larger reserves of energy than the males. Some authors suggest the females and males of certain species apply the resources obtained in feeding differently. Generally, Males expend the extra energy on flight, while females use their food resources to achieve longer lifespans. The respective strategies should be compatible with maximal probability of successful mating and reproduction in those species that do not mate immediately after eclosion, particularly in species that have more than one egg mass maturing, the less developed masses being oviposited after a delay. Such variables also would be relevant to species that exploit wind for dispersal, laying eggs at intervals. Chironomids that feed on nectar or pollen may well be of importance as pollinators, but current evidence on such points is largely anecdotal. However, the content of protein and other nutrients in pollen, in comparison to nectar, might well contribute to the females' reproductive capacities. MIGHT BE PLAGIARISED

Larvae of some species are bright red in color due to a hemoglobin analog; these are often known as "bloodworms". Their ability to capture oxygen is further increased by making undulating movements.

Ecology and Distribution
Chironomids are highly versatile species that can tolerate a very wide range of environmental stresses. They are found in high abundances in many of the habitats they live in, and represent important food sources for a variety of organisms. In addition, they are found representing a significant number of symbiotic relationships with other aquatic insects, terrestrial insects, and some plants.

They are distributed, and in most cases found in high abundance globally, from the Artic to Antarctica. They are found in wide variety of habitats, from the glaciated areas of the tallest mountains, to the deepest bodies of freshwater.

Aquatic habitats
Larval stages of the Chironomidae can be found in almost any aquatic or semiaquatic habitat. In fact, in many freshwater aquatic habitats, especially polluted ones, chironomids are often one of the most abundant insects found. Aquatic habitats can be marine or freshwater, the latter including treeholes, bromeliads, interstitial and benthic zones, as well as man-made sewage and artificial containers. They can also be found inhabiting plant held waters, intertidal zones, interstitial zones. Many species of chironomids are found residing in sediments or benthic levels of water bodies, where Dissolved oxygen is very low.

A number of chironomid species inhabit marine habitats. Midges of the genus Clunio are found in the intertidal zone, where they have adjusted their entire life cycle to the rhythm of the tides. This made the species Clunio marinus an important model species for research in the field of chronobiology.

Terrestrial habitats
Chironomid larvae can also be found in some terrestrial habitats. Many species that are terrestrial are found living in soil as a dominant part of soil fauna community, particularly in wet soil habitats but also in agricultural land and in early stages of succession. Some species will use humic soils to develop as larvae on land; usually using decaying vegetation or sometimes living vegetation to survive. one family of chironomids, Camptocladius are known to develop as larvae in cow dung. There are also some that are known to burrow deep into soil in cases of temporary aquatic habitats or droughts.

Chironomid adults are predominately found in terrestrial habitats.

Roles in the ecosystem
Chironomids have variable feeding ecology: most species feed on algae and other small soil organisms they can filtrate. Some commensal species feed off of algae on their hosts, which also provides the benefit of protection and additional mobility; particularly when their chosen host site is another predatory larval species. Some species are parasitic, and pierce the integument of its host in order to feed off of its hemolymph.

Larvae and pupae are important food items for fish, such as trout, banded killifish, and sticklebacks, and for many other aquatic organisms as well such as newts. Many aquatic insects, such as various predatory hemipterans in the families Nepidae, Notonectidae, and Corixidae eat Chironomidae in their aquatic phases. Additionally, predatory water beetles in families such as the Dytiscidae and Hydrophilidae have been found to feed on larval chironomids. Flying midges in their adult stage are eaten by fish and insectivorous birds, such as swallows and martins. They are also thought to be an especially important food source for tufted duck chicks during their first few days of life. They also are preyed on by bats and flying predatory insects, such as Odonata and dance flies.

They form an important fraction of the macro zoobenthos of most freshwater ecosystems. They are highly tolerant to low dissolved oxygen levels and changing salinity levels, both of which are often resultant from human pollution. Thus, The Chironomidae are important as indicator organisms, i.e., the presence, absence, or quantities of various species in a body of water can indicate whether pollutants are present.

Also, their fossils are widely used by palaeolimnologists and paleoentomologists as potential indicators of past environmental changes, including past climatic variability. Although, the results of these tests are often controversial, and there are disagreements as to how beneficial they can be in the paleoentomology world.

Symbiotic relationships
A significant portion of the Chironomidae larvae have been reported in commensal relationships with other organisms in their ecosystems. Although little is known about host choice and preference, its been reported widely that Ephemeroptera are typically their most commonly reported host sites.

Not all Chironomidae species exhibit these relationship behaviors, and not all individuals within a species may exhibit these behaviors.

These relationships can be

Larval Chironomids often partake in commensal behaviors as a result of limited mobility and defensive morphology. Although they do not have appendages designed for swimming, and most free-living movement is done through undulations, Chironomids do possess strong appendages that help them grasp onto a host.

Larval Commensal chironomids have been known to compete for space on the host. This competition happens on an interspecies level, but also with other commensal and or phoretic organisms. Chironomids have been reported to compete with ciliated protozoan Ephemera danica, although this competition has resulted in niche-partitioning on the hosts body. These species do not compete for food, but rather for ideal spaces on the host. In these competitive relationships, Chironomids generally choose larger host body sizes, while the protozoans might prefer smaller hosts. In host sites that contained both species, potential micro niches were observed, as these organisms were observed to deliberately space themselves out. Generally however, it seemed that chironomids beat out the protozoan in abundance on a host.

Competition for hosts also happens in a major fashion on an interspecific scale. This may differ sesonally,

A number of biotic and abiotic factors may affect host choice in chironomids. There is evidence that this choice is pressured by hydrological factors. A higher number of chironomids associating phoretically with Ephemeroptera during a rainy season. In the dry season, host choices seemed to diversify a great deal, with many hosts only being found in a dry season. It has been suggested that this may be due to an influx of vegetative debri and detritus that characterizes a rainy season in aquatic environments, which would cause an increase in associated taxa, such as Ephemeroptera.

There have been reports of phoretic associates with predatory aquatic insects as well in chironomidae. These relationships, although uncommon, represent more steady hosts for chironomids if they are accessible. Phoresy on a predatory host has been suggested to mean a more mobile, and protective host, resulting in an easier development stage for the commensal organism.

Life Histories and Development
Chironomidae exhibit a diverse set of life histories.

Heat tolerance and anhydrobiosis
Many species of chironomids have adapted high tolerances to desiccation, particularly those inhabiting temporary aquatic habitats or places where droughts frequently occur. Anhydrobiosis, which is the resultant of complete desiccation, is the loss of most or all water in the body. Although its more common in terrestrial species, tolerance for drought within chironomidae is similar in both terrestrial and aquatic species. A species from Africa was found with extreme tolerance to desiccation. This species was able to completely desiccate, and within 48 hours movement was found after rehydration. This same species is able to withstand this pause in development for an extended period of time, with records of it surviving up to 17 years completely dehydrated.

Some can withstand high temperatures without the need to desiccate and pause development. A Japanese species of chironomid, Tokunagayusurika akasumi, have adapted to aestivation in sediments below their habitats in the event of high temperatures.

Cold tolerance
Chironomids as a whole are a relatively cold-tolerant group.

Overwintering of species is found in almost all subfamilies of chironomidae. Most of them cocoon during their pupation to overwinter, but this is not found in all individuals within a species. It is hypothesized that this overwintering difference in behavior occurs when temperature are at their lowest, and perhaps has to do with the presence of ice cover in the habitat.

Others
Larval Chironomidae have also been reported adapting to other extremes in their environments, including pH levels, salinity levels, depth, and water velocity.

Chironomids and humans
Chironomids can be both beneficial and nuisance to humans. In many areas of the world, anglers and aquarium hobbyists use them as bait or a food source, particularly bloodworms. They are also historically important food sources for some communities in Africa.

Some Chironomid larvae thrive in very heavily polluted habitats. These habitats are often man-made, and result in little to no biodiversity, which implies no natural predators present to keep midge populations at natural levels. These conditions often worsen emergence events, which also take place near human dominated habitats.

Adults can be pests when they emerge in large numbers. They may cause difficulty during driving if they collide with the windshield, creating an opaque coating which obscures the driver's vision. They can damage paint, brick, and other surfaces with their droppings. When large numbers of adults die, they can build up into malodorous piles. They can provoke allergic reactions in sensitive individuals. These allergic reactions have been shown to be caused by the haemolglobins that are primarily found in Chironomidae larval stages.