Structural organization of the heart of the mosquito Anopheles gambiae - image

The ''Anopheles gambiae''

complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...

consists of at least seven morphologically indistinguishable species of

mosquitoes Mosquitoes, the Culicidae, are a family of small flies consisting of 3,600 species. The word ''mosquito'' (formed by '' mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mosquitoes have a slender segmented body, ...

in the genus ''

Anopheles ''Anopheles'' () is a genus of mosquito first described by the German entomologist Johann Wilhelm Meigen, J. W. Meigen in 1818, and are known as nail mosquitoes and marsh mosquitoes. Many such mosquitoes are Disease vector, vectors of the paras ...

''. The complex was recognised in the 1960s and includes the most important vectors of

malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...

sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...

, particularly of the most dangerous malaria parasite, ''

Plasmodium falciparum ''Plasmodium falciparum'' is a Unicellular organism, unicellular protozoan parasite of humans and is the deadliest species of ''Plasmodium'' that causes malaria in humans. The parasite is transmitted through the bite of a female ''Anopheles'' mos ...

''. It is one of the most efficient

vectors known. The ''An. gambiae'' mosquito additionally transmits ''

Wuchereria bancrofti ''Wuchereria bancrofti'' is a filarial (arthropod-borne) nematode (roundworm) that is the major cause of lymphatic filariasis. It is one of the three parasitic worms, together with ''Brugia malayi'' and '' B. timori'', that infect the lymphati ...

'' which causes

lymphatic filariasis Lymphatic filariasis is a human disease caused by parasitic worms known as filarial worms. Usually acquired in childhood, it is a leading cause of permanent disability worldwide, impacting over a hundred million people and manifesting itself in ...

, a symptom of which is

elephantiasis Elephantiasis, often incorrectly called elephantitis, is the enlargement and hardening of limbs or body parts due to tissue swelling (edema). It is characterised by edema, hypertrophy, and fibrosis of skin and subcutaneous tissues, due to obstru ...

Discovery and elements

The ''Anopheles gambiae''

or ''Anopheles gambiae''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

was recognized as a species complex only in the 1960s. The ''A. gambiae'' complex consists of: * '' Anopheles arabiensis'' Patton, 1905 * '' Anopheles bwambae'' White, 1985 * '' Anopheles melas'' Theobald, 1903 * '' Anopheles merus'' Dönitz, 1902 * '' Anopheles quadriannulatus'' (Theobald, 1911) * ''Anopheles gambiae'' Giles, 1902

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

(s.s.) * ' Coetzee & Wilkerson in Coetzee et al., 2013 * '' Anopheles amharicus'' Hunt, Wilkerson & Coetzee in Coetzee et al., 2013 The individual species of the complex are morphologically difficult to distinguish from each other, although it is possible for larvae and adult females. The species exhibit different behavioural traits. For example, ''Anopheles quadriannulatus'' is both a saltwater and mineralwater species. ''A. melas'' and ''A. merus'' are saltwater species, while the remainder are freshwater species. ''Anopheles quadriannulatus'' generally takes its blood meal from animals (

zoophilic Zoophily, or zoogamy, is a form of pollination whereby pollen is transferred by animals, usually by invertebrates but in some cases vertebrates, particularly birds and bats, but also by other animals. Zoophilous species frequently have evolved ...

), whereas ''Anopheles gambiae'' sensu stricto generally feeds on humans, i.e. is considered

anthropophilic In parasitology, anthropophilia, from the Greek ἅνθρωπος (anthrōpos, "human being") and φιλία (philia, "friendship" or "love"), is a preference of a parasite or dermatophyte for humans over other animals.Braun-Falco, Otto (2000). ' ...

. Identification to the individual species level using the molecular methods of Scott ''et al.'' (1993) can have important implications in subsequent control measures.

''Anopheles gambiae'' in the strict sense

''An. gambiae sensu stricto'' (s.s.) has been discovered to be currently in a state of diverging into two different species—the Mopti (M) and Savannah (S) strains—though as of 2007, the two strains are still considered to be a single species. A mechanism of species recognition using the sound emitted by the wings and identified by

Johnston's organ Johnston's organ is a collection of sensory cells found in the pedicel (the second segment) of the antennae in the class Insecta. Johnston's organ detects motion in the flagellum (third and typically final antennal segment). It consists of sc ...

was proposed in 2010, however this mechanism has never been confirmed since, and the overall mechanism theory through "harmonic convergence" has been challenged.

Genome

''An. gambiae'' s.s.

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

s have been sequenced three times, once for the M strain, once for the S strain, and once for a hybrid strain. Currently, ~90 miRNA have been predicted in the literature (38 miRNA officially listed in miRBase) for ''An. gambiae'' s.s. based upon

conserved sequence In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids ( DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ...

s to miRNA found in ''

Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...

''. Holt ''et al.'', 2002 and Neafsey ''et al.'', 2016 find

transposable element A transposable element (TE), also transposon, or jumping gene, is a type of mobile genetic element, a nucleic acid sequence in DNA that can change its position within a genome. The discovery of mobile genetic elements earned Barbara McClinto ...

s to be ~13% of the genome, similar to ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...

'' (also in

Diptera 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 advance ...

). However they find the proportion of TE types to be very different from ''D. melanogaster'' with approximately the same composition of long terminal repeat retrotransposons, non-long terminal repeat retrotransposons and

DNA transposon DNA transposons are DNA sequences, sometimes referred to "jumping genes", that can move and integrate to different locations within the genome. They are class II transposable elements (TEs) that move through a DNA intermediate, as opposed to class I ...

s. These proportions are believed to be representative of the genus. The genetics and genomics of

sex chromosome Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, or idiochromosomes) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair ...

s have been discovered and studied by Windbichler ''et al.'', 2007 and Galizi ''et al.'', 2014 (a ''

Physarum polycephalum ''Physarum polycephalum'', an Multinucleate, acellular slime mold or myxomycete popularly known as "the blob", is a protist with diverse cellular forms and broad geographic distribution. The “acellular” moniker derives from the plasmodial s ...

homing endonuclease The homing endonucleases are a collection of endonucleases encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. They catalyze the hydrolysis of genomic DNA within the cells that synthes ...

which destroys

X chromosome The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its u ...

s), Windbichler ''et al.'', 2008 and Hammond ''et al.'', 2016 (methods to reduce the female population), Windbichler ''et al.'', 2011 (

trans Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Sociology * Trans, a sociological term which may refer to: ** Transgender, people who identify themselves with a gender that di ...

from yeast), Bernardini ''et al.'', 2014 (a method to increase the male population), Kyrou ''et al.'', 2018 (a female necessary

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...

and a homing endonuclease to drive it), Taxiarchi ''et al.'', 2019 (sex chromosome dynamics in general) and Simoni ''et al.'', 2020 (an X chromosome destroying site specific nuclease). See below for their applications. ''An. gambiae'' has a high degree of polymorphism. This is especially true in the

cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...

s, Wilding ''et al.'', 2009 finding 1

single nucleotide polymorphism In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in ...

(SNP)/26

base pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s. This species has the highest amount of polymorphism in the CYPs of any insect known, much tending to be found in "scaffolds" that are found only in particular subpopulations. These are termed "dual haplotype regions" by Holt ''et al.'', 2002 who sequenced the strain. In common with many chromosomes, ''An. gambiae'' codes for spindle and kinetochore-associated proteins. Hanisch ''et al.'', 2006 locate '' AgSka1'', the spindle and kinetochore-associated protein 1 gene, at EAL39257. The entire

Culicidae Mosquitoes, the Culicidae, are a Family (biology), family of small Diptera, flies consisting of 3,600 species. The word ''mosquito'' (formed by ''Musca (fly), mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mos ...

family may or may not conserve

epigenetic In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in ...

mechanisms this remains unresolved. Toward answering this question, Marhold ''et al.'', 2004 compare their own previous work in ''

'' against new sequences of '' D. pseudoobscura'' and ''An. gambiae''. They find all three do share the

DNA methylation DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter (genetics), promoter, DNA methylati ...

enzyme DNMT2 ('' DmDNMT2'', '' DpDNMT2'', and '). This suggests all

may conserve an epigenetic system employing Dnmt2.

Hosts

Host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

s include

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

goats The goat or domestic goat (''Capra hircus'') is a species of goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the famil ...

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

and

wild boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a Suidae, suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The speci ...

Parasites

Parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s include '' Plasmodium berghei'' (for which it also serves as a

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

), and the bioinsecticides/ entomopathogenic fungi '' Metarhizium robertsii'' and ''

Beauveria bassiana ''Beauveria bassiana'' is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the group of entomopathogenic fungi. It is used as a ...

''. All three of these parasites combine with

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

s to reduce fitness see below. CRISPR/Cas9 and U6-gRNA are increasingly () being used together for knockout experiments in mosquitoes. Dong ''et al.'', 2018 develops and presents a new U6-gRNA+Cas9 technique in ''An. gambiae'', and utilizes it to knock out fibrinogen related protein 1 (FREP1), thereby severely reducing infection of the mosquito by ''P. berghei'' and '' P. falciparum''. However this also demonstrates the centrality of FREP1 to the insect's success, impairing all measured activities across all life stages. Yang ''et al.'', 2020 uses the Dong method to do the same with '' mosGILT'', also severely reducing ''Plasmodium'' infection of the mosquito but ''also'' finding a vital life process is impaired, in ''mosGILT''s case

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

development.

Control

Insecticides

Parasites/bioinsecticides and chemical insecticides synergistically reduce fitness. Saddler ''et al.'', 2015 finds even ''An. gambiae'' with knockdown resistance (''kdr'') are more susceptible to

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

if they are first infected with '' Plasmodium berghei'' and Farenhorst ''et al.'', 2009 the same for '' Metarhizium robertsii'' or ''

''. This is probably due to an effect found by Félix ''et al.'', 2010 and Stevenson ''et al.'', 2011: ''An. gambiae'' alters various activities especially CYP6M2 in response to ''P. berghei'' invasion. CYP6M2 is known to somehow produce pyrethroid resistance, and pyrethroids and DDT share a

mechanism of action In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical Drug interaction, interaction through which a Medication, drug substance produces its pharmacological effect. A mechanism of action usually includes mention o ...

Gene drive

Research relevant to the development of gene drive controls of ''An. gambiae'' have been performed by Windbichler ''et al.'', 2007, Windbichler ''et al.'', 2008, Windbichler ''et al.'', 2011, Bernardini ''et al.'', 2014, Galizi ''et al.'', 2014, Hammond ''et al.'', 2016, Kyrou ''et al.'', 2018, Taxiarchi ''et al.'', 2019 and Simoni ''et al.'', 2020. For specific genes involved see above. These can all be used in

pest control Pest control is the regulation or management of a species defined as a pest (organism), pest; such as any animal, plant or fungus that impacts adversely on human activities or environment. The human response depends on the importance of the da ...

because they induce

infertility In biology, infertility is the inability of a male and female organism to Sexual reproduction, reproduce. It is usually not the natural state of a healthy organism that has reached sexual maturity, so children who have not undergone puberty, whi ...

Fecundity

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 ...

of ''An. gambiae'' depends on the

detoxification Detoxification or detoxication (detox for short) is the physiological or medicinal removal of toxic substances from a living organism, including the human body, which is mainly carried out by the liver. Additionally, it can refer to the period o ...

reactive oxygen species In chemistry and biology, reactive oxygen species (ROS) are highly Reactivity (chemistry), reactive chemicals formed from diatomic oxygen (), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide (H2O2), superoxide (O2−), hydroxyl ...

(ROS) by

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

. Reduction in catalase activity significantly reduces reproductive output of female mosquitoes, indicating that catalase plays a central role in protecting

oocyte An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...

s and early

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

s from ROS damage.

Historical note

''An. gambiae'' invaded northeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

in 1930, which led to a malaria epidemic in 1938/1939. The Brazilian government assisted by the

Rockefeller Foundation The Rockefeller Foundation is an American private foundation and philanthropic medical research and arts funding organization based at 420 Fifth Avenue, New York City. The foundation was created by Standard Oil magnate John D. Rockefeller (" ...

in a programme spearheaded by Fred Soper eradicated these mosquitoes from this area. This effort was modeled on the earlier success in eradication of ''

Aedes aegypti ''Aedes aegypti'' ( or from Greek 'hateful' and from Latin, meaning 'of Egypt'), sometimes called the Egyptian mosquito, dengue mosquito or yellow fever mosquito, is a mosquito that spreads diseases like dengue fever, yellow fever, malar ...

'' as part of the yellow fever control program. The exact species involved in this epidemic has been identified as '' An. arabiensis''.

Peptide hormones

Kaufmann and Brown 2008 find the ''An. gambiae'' adipokinetic hormone (AKH) mobilizes

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

s but not

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

s. Meanwhile AKH/Corazonin Peptide (ACP) does not mobilize (or inhibit mobilization) of either. Mugumbate ''et al.'', 2013 provides in solution and membrane bound structures from a

nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

investigation.

References

External links

* *
DiArk
{{Authority control gambiae Insect vectors of human pathogens Animal models Insects described in 1902