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Mosquitofish

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Gambusia affinis
Female
Male
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Cyprinodontiformes
Family:
Poeciliidae
Genus:
Gambusia
Species:
G. affinis
Binomial name
Gambusia affinis
(Baird and Girard, 1853)

The mosquitofish (Gambusia affinis) is a species of freshwater fish, also commonly, if ambiguously, known by its generic name, gambusia. It is sometimes called the western mosquitofish, to distinguish it from the eastern mosquitofish (G. holbrooki). It is a member of the family Poeciliidae of order Cyprinodontiformes. The genus name Gambusia is derived from the Cuban Spanish term gambusino, meaning "useless".[2]

Description

Mosquitofish are small, dull grey, have a large abdomen, and have rounded dorsal and caudal fins and an upturned mouth towards the surface.[3] Sexual dimorphism is pronounced; mature females reach a maximum overall length of 7 centimeters (2.8 in), while males reach only 4 centimeters (1.6 in). Sexual dimorphism is also seen in the physiological structures of the body. The anal fins on adult females resemble the dorsal fins, while the anal fins of adult males are pointed. This pointed fin, referred to as a gonopodium, is used to deposit milt inside the female. Adult female mosquitofish can be identified by a gravid spot they possess on the posterior of their abdomen. Other species that are considered similar to G. affinis include, Poecilia latipinna, Poecilia reticulata, Xiphophorus maculatus, and is commonly misconceived as the eastern mosquitofish.[4][3]

Naming and Taxonomy

The common name of the Gambusia affinis is the mosquitofish or western mosquitofish to defferentiate from the eastern mosquitofish, G. holbrooki. This name is derived from the fact that it eats large amounts of mosquito larve. Determining the western mosquitofish's binomial name has been difficult due to the close resemblance in the eastern mosquitofish, and according to ITIS (Integrated Taxonomic Information System), G. holbrooki is an invalid taxonomic name and is rather a subspecies of G. affinis.[3][5]

Diet

Mosquito Larvae.

Diet wise, mosquitofish are classified as larvivorous fish.[6] The diet of mosquitofish mostly consists of zooplankton, small insects and insect larvae, and detritus material. Mosquitofish feed on mosquito larvae at all stages of life. Adult female mosquitofish can consume in one day hundreds of mosquito larvae.[3] Maximum consumption rate in a day by one mosquitofish has been observed to be from 42%-167% of its own body weight.[7] Mosquitofish have also shown cannibalistic behavior in laboratory experiments, however, whether or not these traits are hereditary is unknown.[8]

Habitat

They are most abundantly found in shallow water to protect them from the larger fish.[9] Mosquitofish can survive relatively ihospitable environments, and are resilient to low oxygen concentrations, high salt concentrations (up to twice that of sea water), and temperatures up to 42 °C (108 °F) (for short periods).[4] Because of the mosquitofish's notable adaptability to harsh conditions they are considered to be the most widespread freshwater fish in the world. Another contributor to the mosquitofish's prevalent ocurrence arround the world is human intervention as a biocontrol by lowering mosquito populations.[10] The native range of the mosquitofish ranges from southern parts of Illinois and Indiana, throughout the Mississippi river and it's tributary waters, to as far south to the Gulf Coast in the northeastern parts of Mexico.[11] In the United States, they can be found throughout the southern half of the land in between the Rocky and Appalachian mountains.[1]

Environmental Impacts

Mosquitofish were intentionally introduced in many areas with large mosquito populations so that they might decrease the population of mosquitoes by eating the mosquito larvae.[3] However, most introductions were ill-advised; in most cases native fish had already been proven to supply maximal control of mosquito population and introducing mosquitofish has been more harmful to indigenous aquatic life than to the mosquito population.[10] Intruductions outside the mosquitofish's natural range, can be harmful to the nonnative ecosystems.[12][13] Mosquitofish have been known to kill or injure other small fish by their aggressive behaviour and otherwise harm them through competition.[7] Mosquitofish are now considered just slightly better at eating mosquitoes than at destroying other aquatic species.[4] However, from the 1920's to 1950's, mosquitofish were a major factor in the eradication of malaria in South America, in southern Russia and in Ukraine. A somewhat famous example of mosquitofish eradicating malaria is on the coast of the Black Sea located near a city in Russia called Sochi.[14][10][15] In Sochi, the mosquitofish is commemorated for eradicating malaria by a monument of the fish.[16][17]

Reproduction

Reproduction of the mosquitofish starts by the male forming a slight tube with his gonopodium, or sometimes referred to as a "modified anal fin," by arranging the rays of the gonopodium. The male mosquitofish will then use this tubular "modified anal fin" to secrete milt into the female mosquitofish's genital aperture by breifly making contact with it, thus making fertilization internal.[3][9][18] The female mosquitofish's gental aperture is located just behind the anal and is an opening for the milt to fertilize the ova within the ovary.[9] Mosquitofish are within the infraclass teleostei and as all teleosts mosquitofish lack a uterus so production of oocytes and gestation occur within the ovary of a female mosquitofish.[19][20] Inside the female, sperm from multiple males can be stored to later fertilize more ova.[3] Based off of labratory experiments, the female mosquitofish is believed to be vitellogenic in nature during spring when the average temperature reaches about 14 °C (57 °F), and then the oocytes finish maturing when the average temperature reaches about 18 °C (64 °F). Then late in the summer when the photoperiod is less than 12.5 hours long, the next clutch of oocytes lose vitellogenesis.[19] In one reproductive season a female may fertilize, with stored milt, 2 to 6 broods of embryos, but the size of the brood decreases through the progression of the season.[1]

Embryology

Mosquitofish have been observed to have a 16 to 28 day gestation period.[21] Mosquitofish are lecithotrophic, which means during gestation, nutrients are provided to the embryos by a yolk-sac.[22] If the gestation period is shorter, at birth each new born will still have a yolk-sac connected through a slit located on the ventral side of the body wall.[21] Female mosquitofish vary on capability of brood size depending on the size of the given female; larger females are more capable of a larger brood quantity than smaller females.[1][3] Mosquitofish are viviparous, which means after the gestation of a brood the female will have live birth.[19][18] In most cases the new born brood will have an equal male to female ratio.[1]

Growth

After birth, newborn mosquitofish are about 8 millimeters (0.31 in) to 9 millimeters (0.35 in) in length. Then as jouvinals, they will grow at a rate of about .2 millimeters (0.0079 in) per day. Growth rate of jouvinal mosquitofish is at its peak when the average water temperature is about 24 °C (75 °F) to 30 °C (86 °F), and decreases the hotter or colder the average temperature is until the average temperature reaches the lethal temperature at 35 °C (95 °F) or at temperatures below 10 °C (50 °F) where growth stops.[1]

See also

References

  1. ^ a b c d e f Whiteside, Bobby; Bonner, Timothy; Thomas, Chad; Whiteside, Carolyn. "Gambusia affinis western mosquitofish". Texas State University. Retrieved 25 October 2011.
  2. ^ Wallus & Simon 1990, p. 175
  3. ^ a b c d e f g h Masterson, J. "Gambusia affinis". Smithsonian Institution. Retrieved 21 October 2011.
  4. ^ a b c "Gambusia affinis (fish)". Global Invasive Species Database. Retrieved 21 October 2011.
  5. ^ "Gambusia holbrooki Girard, 1859". ITIS. Retrieved 30 December 2011.
  6. ^ Regional Office For The Eastern Mediterranean 2003, p. 15
  7. ^ a b Nico, Leo; Fuller, Pam; Jacobs, Greg; Cannister, Matt (19 August 2009). "Gambusia affinis". USGS. Retrieved 25 October 2011.
  8. ^ Dionne 1985, pp. 16–23
  9. ^ a b c Kuntz 1913, pp. 181–190
  10. ^ a b c "М.: Советская энциклопедия". Гамбузия. Большая советская энциклопедия (in Russian). Академике. 2000–2010. Retrieved 23 October 2011.{{cite encyclopedia}}: CS1 maint: date format (link)
  11. ^ Krumholz 1944, p. 82
  12. ^ "Aquatic Invasive Species: Gambusia affinis (Mosquito fish)". Washington Department of Fish and Wildlife. Washington Department of Fish and Wildlife. Retrieved 2 January 2012.
  13. ^ Rupp, Henry (1995). "Adverse Assessments of Gambusia affinis". North American Native Fishes Association (NANFA). Retrieved 2 January 2012.
  14. ^ Vinogradova 2000, p. 187
  15. ^ Ильин, Иван. "История человека – история города Сочи" (in Russian). Объявления Сочи: История человека – история города Сочи / 135 лет со дня рождения Сергея Юрьевича Соколова. Retrieved 8 November 2011.
  16. ^ "В Сочи установлен памятник рыбке, спасшей местность от малярии" (Press release) (in Russian). Кавказский узел. июнь 26 2010. Retrieved 8 November 2011. {{cite press release}}: Check date values in: |date= (help)
  17. ^ "Врачу, спасшему Сочи от малярии, поставят памятник" (Press release) (in Russian). ФедералПресс. 22 Июля 2010 (четверг). Retrieved 8 November 2011. {{cite press release}}: Check date values in: |date= (help)
  18. ^ a b Casal, Christine (23 March 1993). "Reproduction of Gambusia affinis". Fish Base. Retrieved 29 December 2011.
  19. ^ a b c E, Kamiya (2000). "Environmental Regulation of Annual Reproductive Cycle in the Mosquitofish, Gambusia affinis". Department of Biology, Faculty of Education, Gifu University, Gifu 501-1193, Japan. PubMed. Retrieved 29 December 2011.
  20. ^ Schindler & Hamlett 1993, pp. 378–393
  21. ^ a b Rajkumar 1987, pp. 32–36
  22. ^ HJ, Grier (2010). "Oogenesis of microlecithal oocytes in the viviparous teleost Heterandria formosa". J. Morphol. Wiley. PMID 21154752.

Bibliography

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