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''Coelopa frigida'' is a species of
seaweed fly Kelp fly is one common name of species of flies in a number of families of "true flies" or Diptera. They generally feed on stranded and rotting seaweed, particularly kelp in the wrack zone. When conditions are suitable they are very numerous and ...
or
kelp fly Kelp fly is one common name of species of flies in a number of Taxonomic rank#Ranks in zoology, families of "true Fly, flies" or Fly, Diptera. They generally feed on stranded and rotting seaweed, particularly kelp in the wrack zone. When condition ...
. It is the most widely distributed species of seaweed fly. It can be found on most shorelines in the temperate Northern Hemisphere. Other species of seaweed flies include ''Coelopa nebularum'' and ''
Coelopa pilipes ''Coelopa pilipes'' (common name kelp fly or seaweed fly) is a common European species of kelp fly. It was species description, described by Alexander Henry Haliday, A. H. Haliday in 1838. Their appearance differs greatly from that of other ''Co ...
''. ''C. frigida'' feeds primarily on seaweed, and groups of ''C. frigida'' flies tend to populate near bodies of water. Climate change has led to an increase in ''C. frigida'' blooms along shores, which creates a pest problem for human beach-goers. ''C. frigida'' is also an important organism for the study of sexual selection, particularly female choice, which is influenced by genetics.


Description

''C. frigida'' are the most common seaweed fly. They tend to aggregate on beaches with an abundance of stranded algae, but occasionally swarm inland. Their physical features include a dark brown to black body, a set of lighter colored legs, and large, translucent wings. Males are typically larger than females, though there is a wide range of adult sizes within the species. ''C. nebularum'' is currently suggested as a close cousin or even possible subspecies of ''C. frigida.'' This article therefore includes specifics regarding ''C. nebularum.''


Distribution

''C. frigida'' are commonly found on beaches with a relatively steady supply of stranded kelp, as the fly species is dependent on the decaying green and brown algae for both feeding and breeding. The geographic range, which is well documented, extends up the North Atlantic Coast into Iceland and encompasses the coasts of
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
, the
North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...
, and
Faroe Islands The Faroe Islands ( ) (alt. the Faroes) are an archipelago in the North Atlantic Ocean and an autonomous territory of the Danish Realm, Kingdom of Denmark. Located between Iceland, Norway, and the United Kingdom, the islands have a populat ...
. Other regions reported to contain ''C. nebularum'' are found on the Pacific Coast of
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, the coast of Japan's
Kuril Islands The Kuril Islands or Kurile Islands are a volcanic archipelago administered as part of Sakhalin Oblast in the Russian Far East. The islands stretch approximately northeast from Hokkaido in Japan to Kamchatka Peninsula in Russia, separating the ...
, and the eastern coasts of Russia.


Habitat

''C. frigida'' need a constant supply of algae to feed and lay their eggs. Thus, coastal beaches with stranded seaweed are their preferred environment. The significant factors that determine the population density and spread are the age of algae, the presence or absence of high winds or storms, the rate of decay of algae, and temperature.


Influence of weather

Research shows that storms and their accompanying harsh weather conditions cause an overall decrease in the life expectancy of ''C. frigida''. Lower temperatures allow for beached seaweed to remain fresh for a longer period of time. Lower temperatures also force ''C. frigida'' to incubate in the egg stage to a greater extent before hatching. Meanwhile, higher temperatures cause an acceleration in the decomposition of algae and also increases the rate of egg development. There has been no significant research done on differentiating the average lifetimes of ''C. frigida'' exposed to different temperatures.


Taxonomy

The first documented discovery of ''C. frigida'' was in 1805 by Fabricius. He called the fly ''frigida'', meaning "cold", presumably from his comment "''Habitat in Norwagiae Lapponis frigoris summi patiens,''" meaning "It lives in Norwegian Lapland, tolerating extreme cold." Throughout history, there have been many additions and changes suggested. Haliday discovered different sizes of ''C. frigida'' on the coast of Ireland and gave them the names: ''C. gravis, C. simplex'', and C ''parvula.'' Stenhammer similarly found the species on the coast of Scandinavia, and dubbed them ''C. nitidula'' and ''C. eximia''. Only after Aldrich and Hennig's revision of the entire Palearctic fauna of ''Coelopa'' did the current standing of nomenclature come to light. Currently, ''C. frigida'' is the official name for this species of fly. There is an ongoing dispute on whether ''C. nebularum'' should be considered a subspecies of ''C. frigida'' or recently speciated species of ''Coelopa''.


Life history


Egg

''C. frigida'''s egg phase is on average 12.25 ± 1.05 days, but changes depending on the presence of
alcohol dehydrogenase Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to N ...
or higher temperatures. Higher temperatures, such as those caused by climate change, may cause eggs to hatch more quickly. The eggs are laid en masse in the leaves of stranded algae.


Adult

The adults emerge from their pupal shells ready to fly in search of mates. Their wings are typically 6 mm and once dry carry them around their current seaweed plot or to other stranded algae. Their bodies are colored a light brown to black, with a few yellow specks. Lastly, their legs are much longer than before
eclosion A pupa (; : 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 life cycle, the stages th ...
and have hooked attachments at the end to better grip onto seaweed. The fly oviposits in dead
kelp Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...
that washes up on
beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from Rock (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological s ...
es. This is the only place it lays eggs, and it can do so on many species of kelp and seaweed, including species of ''
Laminaria ''Laminaria'' is a genus of brown algae, brown seaweed in the order Kelp, Laminariales (kelp), comprising 31 species native to the north Atlantic and northern Pacific Oceans. This economically important genus is characterized by long, leathery L ...
'' and ''
Fucus ''Fucus'' is a genus of brown algae found in the intertidal zones of rocky seashores almost throughout the world. Description and life cycle The thallus is perennial with an irregular or disc-shaped holdfast or with haptera. The erect portion ...
''. A female fly lays up to five clutches of 80 eggs each. The
larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...
e feed upon the
bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
coating the dead kelp. The life cycle is about 30 days long.


Food resources

The main food source for ''C. frigida'' is seaweed that has washed up onto the beaches. The adults detect the scent of the seaweed and lie their eggs in the decaying algae. The seaweed's particular environment allows the eggs to hatch, and the larvae begin to burrow into the seaweed. The brown and green algae preferred by ''C. frigida'' are usually of either the genus '' Lamniaria'' or the genus ''
Fucus ''Fucus'' is a genus of brown algae found in the intertidal zones of rocky seashores almost throughout the world. Description and life cycle The thallus is perennial with an irregular or disc-shaped holdfast or with haptera. The erect portion ...
''. There is still research being done on whether it is the seaweed itself, the microorganisms within it, or a combination of the two that provides the nutrition needed by the ''C. frigida'' larvae. The algae also provides a safe habitat to live in and a perfect moist environment for eggs, which prevents desiccation. Most adults stay in the seaweed patch of their birth until it returns to the ocean, at which point the adults fly in search of alternative algae bunches to feed, live, and mate on.


Morphology

There are four defining characteristics of ''C. frigida''. The first is the size of the body, which ranges from 5 mm to 6 mm. The size of the body depends on the specific alpha or beta alleles associated with chromosomal inversion. The alpha genes causes individuals to grow to a larger size with a "peacock's tail". However, these larger individual typically spend 2-4 more days throughout the development process before becoming adults. The bodies range from a dark brown to black. The second is color of the legs. The legs of ''C. frigida'' are mostly all the same size, with the only difference being in color. The hue of the legs range from a light brown, to yellow, to black. The third and fourth features are their
tergite A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the Anatomical terms of location#Dorsal and ventral, dorsal ('upper') portion of an arthropod segment other than the head. The Anatomical terms of location#Anterior ...
and accompanying bristles. Most individuals of C. frigida have 6 tergites. Their size may differ according to how far along each individual is in their adult life. The color of their tergites is generally dark brown. Lastly, the accompanying bristles on the tergites vary in different lengths. Most are proportional to the overall body or tergite size. The color of such
seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...
e are either black or the color of the attached tergite.


Ecological Adaptations

C. frigida are highly waterproof due to the a collection of hairs that cover their entire exoskeleton. They can easily escape from algae/seaweed beds that are pulled back into the ocean by simply bobbing up to the surface and then flying back to the coast. This waterproofing has been tested by placing adults into a bottle of seawater and shaking vigorously, with the only result observed being still-dry flies emerging from the water.


Mating

Mating behavior in ''C. frigida'' is dictated by larger males attempting to copulate with smaller females. Larger males have an increased mating success rate than their smaller counterparts. Thus, sexual selection tends to favor males that are larger or can latch on to females more tightly. This
sexual selection Sexual selection is a mechanism of evolution in which members of one sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...
for larger males is countered by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
for smaller males. Smaller males have a lower incubation time, and thus are more likely to survive past their developmental age to adulthood. ''C. frigida'' are
polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...
, with females devoting the majority of resources to laying eggs to increase their reproductive success. Meanwhile, the males choose to mate with as many receptive females as possible to increase their
reproductive success Reproductive success is an individual's production of offspring per breeding event or lifetime. This is not limited by the number of offspring produced by one individual, but also the reproductive success of these offspring themselves. Reproduct ...
.


Laboratory studies

This fly is sometimes cultured in the laboratory. Its behavior is studied in an effort to understand
sexual selection Sexual selection is a mechanism of evolution in which members of one sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...
, especially female choice. Studies suggest that female flies of this species prefer larger males to smaller. The species engages in
lekking A lek is an aggregation of male animals gathered to engage in competitive displays and courtship rituals, known as lekking, to entice visiting females which are surveying prospective partners with which to mate. It can also refer to a space us ...
and
sexual conflict Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness (biology), fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms ...
. Females perform rejection behaviors when mounted by males, and may mate with larger males because larger males are more able to force the mating. As females are more likely to successfully reject smaller males, sexual selection favors larger ones. Mating behaviors are genetically influenced, as evidenced by a preference for smaller males among females of a certain
genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...
.


Genetic research

There are two main focuses of genetic research on ''C. frigida''. The first aspect is the differentiation of ''C. frigida'' from similar looking flies and ''C. nebularum''. The second focus is on the chromosomal inversion of certain alleles to produce flies of differing sizes, and natural selection on certain sizes. The initial discovery of ''C. frigida'' was confused due to their variance in size. This dispute was mostly cleared by delving past their physical characteristics into their genetics, in which most of the seaweed flies were found to belong to ''C. frigida''. The only majorly differing genetic line was associated with ''C. nebularum. C. Nebularum'' had only recently speciated from ''C. frigida'' due to geographic differences, thus it is still widely debated if they belong in the same species or if they're close cousins. The
chromosomal inversion An inversion is a chromosome rearrangement in which a segment of a chromosome becomes inverted within its original position. An inversion occurs when a chromosome undergoes a two breaks within the chromosomal arm, and the segment between the two b ...
of the alpha or beta allele in ''C. frigida'' produces a distinct difference in adult size. Individuals homozygous for the alpha allele are physically larger and more developed. They benefit from the physicality with increased longevity and increased
fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the capability to produc ...
. However, these individuals have 2–4 days more in their developmental phases to grow to such an extent. These may be precious days that the seaweed bed is washed back into the ocean, killing the C. frigida. On the other hand, individuals
homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...
for the beta allele are physically smaller. They benefit by growing into their adult phase faster, but have more trouble finding receptive mates.


Enemies

''C. frigida'' competes with another seaweed fly, ''C. pilipes'', for resources. One might think that the number one predator of C. frigida would be birds such as sandpipers. Seabirds (including the
purple sandpiper The purple sandpiper (''Calidris maritima'') is a small shorebird in the sandpiper family Scolopacidae. This is a hardy sandpiper that breeds in the arctic and subarctic regions of Eurasia and North America and winters further south on the Atlan ...
, ''Calidris maritima'') do eat adult flies; however, these birds only peck within the first few inches of the seaweed and don't penetrate deep enough to get to the eggs and larvae. On the other hand, insects from the Coleoptera and Hymenoptera order have been found to eat C. frigida eggs and larvae in laboratory conditions. More research needs to be done to conclude their presence in the seaweed and their feeding habits. ''C. frigida'' is also host to the
mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...
'' Thinoseius fucicola''.


Human interaction

Typically, the
leks Lek or LEK may refer to: * Lek mating, of animals * Albanian lek, currency * Lek (magazine), Norway * Lek (pharmaceutical company), now part of Sandoz * Lek (river), Netherlands * De Lek, Netherlands fiefdom * L.E.K. Consulting, firm * Leung ...
that ''C. frigida'' form stay within their optimal environment of seaweed patches. However, due to increasing temperatures and more frequent storms resulting from
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, more algae is washed ashore and accompanying it is an increase in the population density of ''C. frigida''. "Blooms" of the flies can occur, possibly when temperatures and amounts of kelp increase. These aggregations are known to pester and annoy beachgoers, but may also be blown inland to city dwellers.


References


Further reading

* {{Taxonbar, from=Q5140675 Coelopidae Diptera of Europe Insects described in 1805 Taxa named by Johan Christian Fabricius