Killifish

Source: Wikipedia, the free encyclopedia.
A bluefin notho killifish, Nothobranchius rachovii, from East Africa

A killifish is any of various

Kryptolebias marmoratus, can additionally survive out of the water for several weeks.[3]
Most killies are small fish, from 2.5 to 5 centimetres (1 to 2 in), with the largest species growing to just under 15 centimetres (6 in).

The word killifish is of uncertain origin, but is likely to have come from the Dutch kil for a kill (small stream).[4] Although killifish is sometimes used as an English equivalent to the taxonomical term Cyprinodontidae, some species belonging to that family have their own common names, such as the pupfish and the mummichog.

Range and habitat

Devils Hole pupfish, Cyprinodon diabolis, from Death Valley National Park

Killifish are found mainly in fresh or brackish waters in the Americas, as far south as Argentina and as far north as southern Ontario and even Newfoundland and Labrador.[5] There are also species in southern Europe, in much of Africa as far south as KwaZulu-Natal, South Africa, in the Middle East and Asia (as far east as Vietnam), and on several Indian Ocean islands.

The majority of killifish are found in permanent streams, rivers, and lakes, and live between two and three years. Such killifish are common in the Americas (Cyprinodon, Fundulus and Rivulus) as well as in Africa and Asia (including Aphyosemion, Aplocheilus, Epiplatys, Fundulopanchax and Lacustricola) and southern Europe (Aphanius). Some of these habitats can be rather extreme; the only natural habitat of the Devils Hole pupfish (Cyprinodon diabolis) is Devils Hole: a cavern at least 91 metres (299 ft) deep, branching out from a small opening at the surface, approximately 1.8 metres (6 ft) by 5.5 metres (18 ft) wide.

Some specialized forms live in temporary ponds and flood plains, and typically have a much shorter lifespan. Such species, known as "annuals", live no longer than nine months, and are used as models for studies on aging. Examples include the African genus

Terranatos
.

Territorial behaviour

topminnow

A small number of species will shoal while most are territorial to varying degrees. Populations can be dense and territories can shift quickly, especially for species of the extreme shallows (a few centimetres of water). Many species exist as passive tribes in small streams where dominant males will defend a territory while allowing females and immature males to pass through the area. In the aquarium, territorial behaviour is different for every grouping, and will even vary by individuals. In a large enough aquarium, most species can live in groups as long as there are more than three males.

Diet

Killifish feed primarily on aquatic arthropods such as insect (

Jordanella floridae) feeds heavily on algae and other plant matter as well as aquatic invertebrates. Nothobranchius furzeri needs much food because it grows quickly, so when food supplied is inadequate, bigger fish will eat the smaller fish.[7]

In lifespan research

A male Nothobranchius furzeri GRZ
(from Gonarezhou National Park)

Some strains have a lifespan as short as several months and can thus serve as a model for biogerontological studies.[8][9][10][11][12] The African turquoise killifish (Nothobranchius furzeri) is the shortest-living vertebrate that can be bred in captivity, having a lifespan of between three and nine months.[9][10] Sexual maturation occurs within 3–4 weeks, with fecundity peaking in 8–10 weeks.[13]

neurodegeneration), and there is an increased risk of cancer with age.[13] Calorie restriction reduces these age-related disease conditions.[13] Resveratrol has been shown to increase the mean (56%) and maximum life span (59%) of Nothobranchius furzeri,[16][17] but resveratrol has not been shown to have this effect in mammals.[18][19][16]

Transferring the gut microbiota from young killifish into middle-aged killifish significantly extends the lifespans of the middle-aged killifish.[20][21]

Transgenic strains have been made,[22] and precise genome editing was achieved in Nothobranchius furzeri using a draft genome and the CRISPR/Cas9 system.[10] By targeting multiple genes, including telomerase, the killifish can now be used as an attractive vertebrate model organism for aging and diseases (such as Dyskeratosis congenita).[10] Sequencing the whole killifish genome indicated modification to the IGF-1 receptor gene.[23]

As pets

Blue lyretail, Fundulopanchax gardneri, one of the most common West African species of killifish kept in aquariums

Many killifish are lavishly coloured and most species are easy to keep and breed in an aquarium. Specimens can be obtained from specialist societies and associations. Striped panchax (also known as the Golden Wonder killifish) are commonly found in pet shops, but caution must be exercised when considering tank mates, since the mouth of the Striped panchax is as wide as the head, and much smaller fish will be eaten. Flagfish, native to south Florida, is another species of killifish commonly found in pet stores. They are useful in aquariums for algae control. The golden topminnow (Fundulus chrysotus) is also native to the United States and often available at auction, but care must be taken with these fish to stop them from jumping out of the tank. A firm cover and a layer of floating plants is best when keeping these fish.

Behaviour-altering infection

Normally, killifish avoid near-surface water to reduce the danger of being eaten by predators. However, when infected with a type of fluke the fish swim near the surface, and sometimes even swim upside down, exposing their camouflaged bellies. The fluke completes its lifecycle in the digestive tract of birds.[24]

Evolved resistance to extreme levels of toxicity

The large populations of killifish and the

Superfund sites. Over a few dozen generations of killifish[25][26] in a relatively short period of time (50–60 years), killifish have evolved resistance against levels of dioxins, PCBs, mercury, and other industrial chemicals up to 8,000 times higher than the previously estimated lethal dose. Sequencing the genomes of the adapted individuals showed a common set of mutations among the pollution-tolerant fish, many of which help to deactivate or turn off a molecular pathway responsible for a large part of the cellular damage caused by the chemicals.[27]

Killifish were found to fare relatively well in the wake of the Deepwater Horizon oil spill.[28][29]

References

  1. S2CID 225478064
    .
  2. ^ List of Nominal Species of Rivulidae (Rivulines)FishBase. Ed. Rainer Froese and Daniel Pauly. May 2007 version. N.p.: FishBase, 2007. Archived 2007-09-30 at the Wayback Machine
  3. ^ "Tropical fish can live for months out of water", Reuters, Wed Nov 14, 2007 9:05pm GMT
  4. ISBN 9789089641243
    .
  5. St. John's, Newfoundland notes, that the Newfoundland population of fundulus diaphanous (banded killifish) is listed as species of Special Concern under Canada's Species at Risk Act
    .
  6. doi:10.11646/zootaxa.1067.1.1
    . Retrieved 4 April 2022.
  7. ^ "Species File: Nothobranchius furzeri". Killi.co.uk. 2009–2013. Retrieved 2013-02-08.
  8. PMID 19052641
    .
  9. ^
    PMID 22384364
    .
  10. ^
    PMID 25684364
    .
  11. PMID 26659161
    .
  12. S2CID 3963445
    .
  13. ^
    PMID 26839399
    .
  14. S2CID 10813587
    .
  15. S2CID 11729069
    .
  16. ^
    S2CID 36628503
    .
  17. S2CID 1662390
    .
  18. PMID 25640851
    .
  19. PMID 22451473
    .
  20. PMID 28826469
    .
  21. PMID 31403049
    .
  22. PMID 22384364
    .
  23. PMID 26638078
    .
  24. ^ "Mindsuckers - National Geographic Magazine". Archived from the original on 2016-04-26. Retrieved 2016-04-26.
  25. S2CID 219039865
    . Retrieved 4 April 2022.
  26. PMID 27959669
    .
  27. ^ Konkel, Lindsey (8 December 2016). "These Fish Evolved to Live in Extremely Toxic Water". National Geographic. University of California, Davis. Archived from the original on December 10, 2016.
  28. ^ "After Deepwater Horizon spill: Which animals weathered the disaster". www.sciencedaily.com. Rutgers University. March 13, 2017. Retrieved March 15, 2017.
  29. doi:10.1002/fee.1474
    .

External links
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