Flea
Fleas Temporal range:
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Scanning electron micrograph | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Clade: | Aparaglossata |
Superorder: | Panorpida |
(unranked): | Antliophora
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Order: | Siphonaptera Latreille, 1825 |
Suborders | |
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Synonyms | |
Aphaniptera |
Flea, the common name for the
Genetic evidence indicates that fleas are a specialised lineage of parasitic scorpionflies (Mecoptera) sensu lato, most closely related to the family Nannochoristidae. The earliest known fleas lived in the Middle Jurassic; modern-looking forms appeared in the Cenozoic. Fleas probably originated on mammals first and expanded their reach to birds. Each species of flea specializes, more or less, on one species of host: many species of flea never breed on any other host; some are less selective. Some families of fleas are exclusive to a single host group; for example, the Malacopsyllidae are found only on armadillos, the Ischnopsyllidae only on bats, and the Chimaeropsyllidae only on elephant shrews.
The oriental rat flea,
Fleas appear in human culture in such diverse forms as flea circuses; poems, such as John Donne's erotic "The Flea"; works of music, such as those by Modest Mussorgsky; and a film by Charlie Chaplin.
Morphology and behavior
Fleas are wingless insects, 1.5 to 3.3 millimetres (1⁄16 to 1⁄8 inch) long, that are agile, usually dark colored (for example, the reddish-brown of the cat flea), with a proboscis, or stylet, adapted to feeding by piercing the skin and sucking their host's blood through their epipharynx. Flea legs end in strong claws that are adapted to grasp a host.[1]
Unlike other insects, fleas do not possess compound eyes but instead only have simple eyespots with a single biconvex lens; some species lack eyes altogether.[2] Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body. The flea body is covered with hard plates called sclerites.[1] These sclerites are covered with many hairs and short spines directed backward, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by scratching.[3]
Fleas lay tiny, white, oval eggs. The larvae are small and pale, have bristles covering their worm-like bodies, lack eyes, and have mouth parts adapted to chewing. The larvae feed on organic matter, especially the feces of mature fleas, which contain dried blood. Adults feed only on fresh blood.[4]
Jumping
Their legs are long, the hind pair well adapted for jumping; a flea can jump vertically up to 18 cm (7 in) and horizontally up to 33 cm (13 in),[5] making the flea one of the best jumpers of all known animals (relative to body size), second only to the froghopper. A flea can jump 60 times its length in height and 110 times its length in distance (vertically up to 7 inches and horizontally 13 inches). That's equivalent to a 1.8 m (6 ft) adult human jumping 360 ft vertically and 660 ft horizontally. Rarely do fleas jump from dog to dog. Most flea infestations come from newly developed fleas from the pet's environment.[6] The flea jump is so rapid and forceful that it exceeds the capabilities of muscle, and instead of relying on direct muscle power, fleas store muscle energy in a pad of the elastic protein named resilin before releasing it rapidly (like a human using a bow and arrow).[7] Immediately before the jump, muscles contract and deform the resilin pad, slowly storing energy which can then be released extremely rapidly to power leg extension for propulsion.[8] To prevent premature release of energy or motions of the leg, the flea employs a "catch mechanism".[8] Early in the jump, the tendon of the primary jumping muscle passes slightly behind the coxa-trochanter joint, generating a torque which holds the joint closed with the leg close to the body.[8] To trigger jumping, another muscle pulls the tendon forward until it passes the joint axis, generating the opposite torque to extend the leg and power the jump by release of stored energy.[8] The actual take off has been shown by high-speed video to be from the tibiae and tarsi rather than from the trochantera (knees).[7]
Life cycle and development
Fleas are holometabolous insects, going through the four lifecycle stages of egg, larva, pupa, and imago (adult). In most species, neither female nor male fleas are fully mature when they first emerge but must feed on blood before they become capable of reproduction.[3] The first blood meal triggers the maturation of the ovaries in females and the dissolution of the testicular plug in males, and copulation soon follows.[9] Some species breed all year round while others synchronise their activities with their hosts' life cycles or with local environmental factors and climatic conditions.[10] Flea populations consist of roughly 50% eggs, 35% larvae, 10% pupae, and 5% adults.[5]
Egg
The number of eggs laid depends on species, with batch sizes ranging from two to several dozen. The total number of eggs produced in a female's lifetime (fecundity) varies from around one hundred to several thousand. In some species, the flea lives in the host's nest or burrow and the eggs are deposited on the substrate,[9] but in others, the eggs are laid on the host itself and can easily fall off onto the ground. Because of this, areas where the host rests and sleeps become one of the primary habitats of eggs and developing larvae. The eggs take around two days to two weeks to hatch.[5]
Larva
Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, faeces, conspecific eggs, and vegetable matter. In laboratory studies, some dietary diversity seems necessary for proper larval development. Blood-only diets allow only 12% of larvae to mature, whereas blood and yeast or dog chow diets allow almost all larvae to mature.[11] Another study also showed that 90% of larvae matured into adults when the diet included nonviable eggs.[12] They are blind and avoid sunlight, keeping to dark, humid places such as sand or soil, cracks and crevices, under carpets and in bedding.[13] The entire larval stage lasts between four and 18 days.[14]
Pupa
Given an adequate supply of food, larvae
Adult
Once the flea reaches adulthood, its primary goal is to find blood and then to reproduce.
Adult female rabbit fleas, Spilopsyllus cuniculi, can detect the changing levels of cortisol and corticosterone hormones in the rabbit's blood that indicate it is getting close to giving birth. This triggers sexual maturity in the fleas and they start producing eggs. As soon as the baby rabbits are born, the fleas make their way down to them and once on board they start feeding, mating, and laying eggs. After 12 days, the adult fleas make their way back to the mother. They complete this mini-migration every time she gives birth.[17]
Taxonomy and phylogeny
History
Between 1735 and 1758, the Swedish naturalist
External phylogeny
It was historically unclear whether the Siphonaptera are sister to the
Relationships of Siphonaptera per Tihelka et al. 2020.[23]
Antliophora
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Fossil history
Fleas likely descended from
Siphonaptera is a relatively small order of insects: members of the order undergo complete metamorphosis and are secondarily wingless (their ancestors had wings which modern forms have lost). In 2005, Medvedev listed 2005 species in 242 genera, and despite subsequent descriptions of new species, bringing the total up to around 2500 species,[20] this is the most complete database available. The order is divided into four infraorders and eighteen families. Some families are exclusive to a single host group; these include the Malacopsyllidae (armadillos), Ischnopsyllidae (bats) and Chimaeropsyllidae (elephant shrews).[26]
Many of the known species are little studied. Some 600 species (a quarter of the total) are known from single records. Over 94% of species are associated with mammalian hosts, and only about 3% of species can be considered to be specific parasites of birds. The fleas on birds are thought to have originated from mammalian fleas; at least sixteen separate groups of fleas switched to avian hosts during the evolutionary history of the Siphonaptera. Occurrences of fleas on reptiles is accidental, and fleas have been known to feed on the hemolymph (bloodlike body fluid) of ticks.[26]
Internal phylogeny
Flea phylogeny was long neglected, the discovery of homologies with the parts of other insects being made difficult by their extreme specialization. Whiting and colleagues prepared a detailed molecular phylogeny in 2008, with the basic structure shown in the cladogram. The Hectopsyllidae, including the harmful chigoe flea or jigger, is sister to the rest of the Siphonaptera.[20]
Siphonaptera |
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Taxonomy
As of 2023[update], there are 21 recognized families within the order Siphonaptera, 3 of which are extinct.[27] In addition, some researchers have suggested that the subfamily Stenoponiinae should be elevated to its own family (Stenoponiidae).[28]
- AncistropsyllidaeToumanoff & Fuller, 1947
- Ceratophyllidae Dampf, 1908
- Chimaeropsyllidae Ewing & I. Fox, 1943
- Coptopsyllidae Wagner, 1928
- Ctenophthalmidae Rothschild, 1915
- Hystrichopsyllidae Tiraboschi, 1904
- Ischnopsyllidae Wahlgren, 1907
- Leptopsyllidae Rothschild & Jordan, 1915
- Lycopsyllidae Baker, 1905
- Malacopsyllidae Baker, 1905
- Pseudopulicidae† Gao, Shih & Ren, 2012
- Pulicidae Billberg, 1820
- Pygiopsyllidae Wagner, 1939
- Rhopalopsyllidae Oudemans, 1909
- Saurophthiridae† Ponomarenko, 1986
- Stephanocircidae Wagner, 1928
- Stivaliidae Mardon, 1978
- Tarwiniidae† Huang, Engel, Cai & Nel, 2013
- TungidaeFox, 1925
- Vermipsyllidae Wagner, 1889
- Xiphiopsyllidae Wagner, 1939
Relationship with host
Fleas feed on a wide variety of warm-blooded vertebrates including dogs, cats, rabbits, squirrels, ferrets, rats, mice, birds, and sometimes humans. Fleas normally specialise in one host species or group of species, but can often feed but not reproduce on other species. Ceratophyllus gallinae affects poultry as well as wild birds.[29] As well as the degree of relatedness of a potential host to the flea's original host, it has been shown that avian fleas that exploit a range of hosts, only parasitise species with low immune responses. In general, host specificity decreases as the size of the host species decreases. Another factor is the opportunities available to the flea to change host species; this is smaller in colonially nesting birds, where the flea may never encounter another species, than it is in solitary nesting birds. A large, long-lived host provides a stable environment that favours host-specific parasites.[30]
Although there are species named dog fleas (Ctenocephalides canis Curtis, 1826) and cat fleas (Ctenocephalides felis), fleas are not always strictly species-specific. A study in Virginia examined 244 fleas from 29 dogs: all were cat fleas. Dog fleas had not been found in Virginia in more than 70 years, and may not even occur in the US, so a flea found on a dog is likely a cat flea (Ctenocephalides felis).[31][32]
One theory of human hairlessness is that the loss of hair helped humans to reduce their burden of fleas and other ectoparasites.[33]
Direct effects of bites
In many species, fleas are principally a nuisance to their hosts, causing an
As a vector
Fleas are
Relationship with humans
In literature and art
Fleas have appeared in poetry, literature, music and art; these include Robert Hooke's drawing of a flea under the microscope in his pioneering book Micrographia published in 1665,[40] poems by Donne and Jonathan Swift, works of music by Giorgio Federico Ghedini and Modest Mussorgsky, a play by Georges Feydeau, a film by Charlie Chaplin, and paintings by artists such as Giuseppe Crespi, Giovanni Battista Piazzetta, and Georges de La Tour.[41]
John Donne's erotic metaphysical poem "
The comic poem Siphonaptera was written in 1915 by the mathematician Augustus De Morgan, It describes an infinite chain of parasitism made of ever larger and ever smaller fleas.[43]
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Robert Hooke's drawing of a flea in Micrographia, 1665
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Development of the flea from egg to adult. Antonie van Leeuwenhoek, c. 1680
Flea circuses
Carriers of plague
Oriental rat fleas, Xenopsylla cheopis, can carry the coccobacillus Yersinia pestis. The infected fleas feed on rodent vectors of this bacterium, such as the black rat, Rattus rattus, and then infect human populations with the plague, as has happened repeatedly from ancient times, as in the Plague of Justinian in 541–542.[46] Outbreaks killed up to 200 million people across Europe between 1346 and 1671.[47] The Black Death pandemic between 1346 and 1353 likely killed over a third of the population of Europe.[48]
Because fleas carry plague, they have seen service as a
The Rothschild Collection
The banker
Flea treatments
Fleas have a significant economic impact. In America alone, approximately $2.8 billion is spent annually on flea-related veterinary bills and another $1.6 billion annually for flea treatment with pet groomers. Four billion dollars is spent annually for prescription flea treatment and $348 million for flea pest control.[13]
See also
References
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- ^ a b Fleas. Koehler, P.G.; Oi, F.M. Printed July 1993, revised February 2003. Provided by the University of Florida
- ^ "Order Siphonaptera – Fleas". BugGuide.Net. Retrieved 11 November 2016.
- ^ a b c d Crosby, J.T. "What is the Life Cycle of the Flea?". Veterinary Parasites. About Home. Retrieved 4 November 2016.
- ^ "Fleas and Ticks: Facts about Fleas". mypet. Merck Animal Health. Retrieved 21 March 2022.
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- ^ "Flea Life Cycle: Eggs, Larvae, etc". Orkin.com. 11 April 2018. Retrieved 13 September 2019.
- ^ Koehler, P.G.; Pereira, R.M.; Diclaro, J.W. "Fleas". Edis.ifas.ufl.edu. Retrieved 11 November 2016.
- ^ a b "How long is the life span of a flea?". Everyday Mysteries: Fun Science Facts from the Library of Congress. Loc.gov. 2 July 2013. Retrieved 11 November 2016.
- ^ a b Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
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- ^ Meyer, John R. (28 March 2016). "Siphonaptera". North Carolina State University. Retrieved 3 December 2016.
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Recently, a close affinity between Siphonaptera and Mecoptera has been convincingly demonstrated via morphology (Bilinski et al. 1998) and molecular data (Whiting 2002), rendering Mecoptera paraphyletic, but making the clade including Mecoptera and Siphonaptera monophyletic
- ^ S2CID 234423213.
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- ^ Eckerlin, Ralph P. (2011). "WHAT KIND OF FLEAS DOES YOUR DOG HAVE?" (PDF). Banisteria. 37: 42–43.
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- ^ "The Project Gutenberg eBook of A Budget of Paradoxes, Volume II (of II), by Augustus de Morgan". gutenberg.org. Retrieved 30 October 2019.
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- ^ "The rise and demise of the flea circus". Natural Histories. BBC Radio 4. Retrieved 2 November 2016.
- ISBN 978-0-670-03855-8.
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- ^ Bossi, P.; et al. (2004). "Bichat guidelines for the clinical management of plague and bioterrorism-related plague". Eurosurveillance. 9 (12): Article 12.
- ^ "Charles Rothschild". The Wildlife Trusts. Retrieved 1 November 2016.
- ^ Sullivan, Walter (10 April 1984). "Miriam Rothschild Talks of Fleas". The New York Times. Retrieved 1 November 2016.
- ^ "Siphonaptera collections". Natural History Museum, London. Retrieved 1 November 2016.