Mangrove rivulus

Mangrove rivulus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Aplocheilidae
Genus: Kryptolebias
Species: K. marmoratus
Binomial name
Kryptolebias marmoratus
Poey, 1880
Synonyms

Rivulus marmoratus

The mangrove killifish or mangrove rivulus, Kryptolebias marmoratus (syn. Rivulus marmoratus),[2] is a species of fish in the Aplocheilidae family. It lives in brackish and marine waters (less frequently in fresh water) along the coasts of Florida, through the Antilles, and along the eastern and northern coasts of Mexico, Central America and South America (south to Brazil).[1][3] It has a very wide tolerance of both salinity (0—68 ‰)[4] and temperature (12–38 °C or 54–100 °F),[5] can survive for about two months on land,[6] and mostly breeds by self-fertilization.[7] It is typically found in areas with red mangrove and sometimes lives in burrows of Cardisoma guanhumi crabs.[5]

The mangrove rivulus is up to 7.5 cm (3.0 in) long,[3] but most individuals are 1–3.8 cm (0.4–1.5 in).[4]

Overall the mangrove rivulus is widespread and not threatened,[1] but in the United States it is considered a Species of Concern by the National Marine Fisheries Service.[8]

Ecology

Land living

The mangrove rivulus can spend up to 66 consecutive days out of water, which it typically spends inside fallen logs, breathing air through its skin.[6] It enters burrows created by insects inside trees where it relaxes its territorial, aggressive behavior. During this time, it alters its gills so it can retain water and nutrients, while nitrogen waste is excreted through the skin. The change is reversed once it re-enters the water.[6][9]

When jumping on land, the mangrove rivulus does a "tail flip", flipping its head over its body towards the tail end. The rivulus' jumping technique gives it an ability to direct its jumps on land and to make relatively forceful jumps. A team of scientists associated with the Society for Experimental Biology released a video in 2013 showing the jumping technique.[10]

Breeding

Mangrove rivulus in Guadeloupe

The species consists mostly of hermaphrodites which are known to reproduce by self-fertilization, but males do exist,[7] and strong genetic evidence indicates occasional outcrossing.[11] They are also the only simultaneous hermaphroditic vertebrates, and the concentration of males to hermaphrodites can vary depending on the local requirement for genetic diversity (for example, if an increase in the local parasite population occurred, secondary male numbers might increase).[12] In Florida, almost all (>99%) are homozygous clones, but in highly colonized South and Central American pools males typically are 3—8% of the population, and in offshore cays in Belize 20—25% are males.[5]

K. marmoratus produces eggs and sperm by meiosis and routinely reproduces by self-fertilization. Each individual hermaphrodite normally fertilizes itself when an egg and sperm that it has produced by an internal organ unite inside the fish’s body.[13] In nature, this mode of reproduction can yield highly homozygous lines composed of individuals so genetically uniform as to be, in effect, identical to one another.[14][15] The capacity for selfing in these fishes has apparently persisted for at least several hundred thousand years.[16] Meioses that lead to self-fertilization can reduce genetic fitness by causing inbreeding depression. However, self-fertilization does provide the benefit of “fertilization assurance” (reproductive assurance) at each generation.[14] Meiosis can also provide the adaptive benefit of efficient recombinational repair of DNA damages during formation of germ cells at each generation.[17] This benefit may have prevented the evolutionary replacement of meiosis and selfing by a simpler type of clonal reproduction such as ameiotic or apomictic parthenogenesis.

Conservation

Overall the mangrove rivulus is widespread and not threatened,[1] but in the United States it is considered a Species of Concern by the National Marine Fisheries Service.[8] It is considered a species of Least Concern by the IUCN,[1] and was formerly listed as a species of special concern in Florida, but has since been delisted.[4] It was formerly often overlooked and considered rare in Florida, but surveys have revealed that it is locally common in this state and abundant in the Florida Keys.[1] It is considered vulnerable by the American Fisheries Society.

The mangrove rivulus is considered to have potential as a bioindicator species of estuary habitats.[1]

See also

References

  1. 1 2 3 4 5 6 7 NatureServe (2014). "Kryptolebias marmoratus". IUCN Red List of Threatened Species. Version 2017.1. International Union for Conservation of Nature. Retrieved 6 May 2017.
  2. ↑ Ong, K. J.; Stevens, E. D.; Wright, P. A. (2007). "Gill morphology of the mangrove killifish (Kryptolebias marmoratus) is plastic and changes in response to terrestrial air exposure". Journal of Experimental Biology. 210 (7): 1109. PMID 17371909. doi:10.1242/jeb.002238.
  3. 1 2 Froese, Rainer and Pauly, Daniel, eds. (2017). "Kryptolebias marmoratus" in FishBase. May 2017 version.
  4. 1 2 3 Bester, C: Mangrove Rivulus. Florida Museum. Retrieved 6 May 2017.
  5. 1 2 3 Hill, K: Rivulus marmoratus. Smithsonian Marine Station at Fort Pierce. Retrieved 6 May 2017.
  6. 1 2 3 "Tropical fish can live for months out of water", Reuters, Wed Nov 14, 2007 9:05pm GMT
  7. 1 2 Lublnski, B. A.; Davis, W. P.; Taylor, D. S.; Turner, B. J. (1995). "Outcrossing in a Natural Population of a Self-Fertilizing Hermaphroditic Fish" (PDF). The Journal of Heredity. 86 (6): 469–473.
  8. 1 2 National Marine Fisheries Service (23 February 2017). Species of Concern List. Retrieved 6 May 2017.
  9. ↑ "The fish that can survive for months in a tree", Daily Mail, 17 October 2007
  10. ↑ "Tail-Flipping Fish Hops on Land - Video". Not available anymore.
  11. ↑ MacKiewicz, M.; Tatarenkov, A.; Turner, B. J.; Avise, J. C. (2006). "A mixed-mating strategy in a hermaphroditic vertebrate". Proceedings of the Royal Society B: Biological Sciences. 273 (1600): 2449. PMC 1634907 Freely accessible. PMID 16959634. doi:10.1098/rspb.2006.3594.
  12. ↑ Cole, Kathleen S.; Noakes, David L. G. (1 January 1997). "Gonadal Development and Sexual Allocation in Mangrove Killifish, Rivulus marmoratus (Pisces: Atherinomorpha)". Copeia. 1997 (3): 596–600. JSTOR 1447566. doi:10.2307/1447566.
  13. ↑ Sakakura, Y., Soyano, K., Noakes, D.L.G. & Hagiwara, A. (2006). Gonadal morphology in the self-fertilizing mangrove killifish, Kryptolebias marmoratus. Ichthyological Research, Vol. 53, pp. 427-430
  14. 1 2 Avise JC, Tatarenkov A (November 2012). "Allard's argument versus Baker's contention for the adaptive significance of selfing in a hermaphroditic fish". Proc. Natl. Acad. Sci. U.S.A. 109 (46): 18862–7. PMC 3503157 Freely accessible. PMID 23112206. doi:10.1073/pnas.1217202109.
  15. ↑ Earley RL, Hanninen AF, Fuller A, Garcia MJ, Lee EA (December 2012). "Phenotypic plasticity and integration in the mangrove rivulus (Kryptolebias marmoratus): a prospectus". Integr. Comp. Biol. 52 (6): 814–27. PMC 3501102 Freely accessible. PMID 22990587. doi:10.1093/icb/ics118.
  16. ↑ Tatarenkov A, Lima SM, Taylor DS, Avise JC (August 2009). "Long-term retention of self-fertilization in a fish clade". Proc. Natl. Acad. Sci. U.S.A. 106 (34): 14456–9. PMC 2732792 Freely accessible. PMID 19706532. doi:10.1073/pnas.0907852106.
  17. ↑ Harris Bernstein, Carol Bernstein and Richard E. Michod (2011). Meiosis as an Evolutionary Adaptation for DNA Repair. Chapter 19 in DNA Repair. Inna Kruman editor. InTech Open Publisher. doi:10.5772/25117
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