Slime coat explained

The slime coat (also fish slime, mucus layer or slime layer) is the coating of mucus covering the body of all fish. An important part of fish anatomy, it serves many functions, depending on species, ranging from locomotion, care and feeding of offspring, to resistance against diseases and parasites.[1]

The mucin making up the slime coat is secreted by goblet cells in the fish's epidermis.[2] The slime contains a variety of antimicrobial peptides and other antimicrobial components such as lysozyme and C-reactive protein.[3] [4] It contains mycosporine-like amino acids to protect from ultraviolet radiation.

Locomotion

The slime coat of some fish aids in more efficient swimming by reducing drag,[5] attributed to the Toms effect.[6] [7] Slime can reduce the friction experienced by the fish by up to 65%.[8] Generally, the faster the fish, the greater reduction in drag provided by the slime, but there are a few exceptions.[9]

In schooling fish, slime shed by leading fish is thought to provide a hydrodynamic benefit to following fish.[10]

As a defensive adaptation

The slime coat of reef fish contains mycosporine-like amino acids (MAAs) which protect the fish from sun damage by absorbing radiation. The greatest number of MAAs is found on the dorsal side of the fish, which is exposed to more radiation.[11] Animals cannot synthesize MAAs, requiring fish to sequester them from their diet.[12]

Under water, fish are exposed to a greater number of microorganisms than animals whose skin is exposed mainly to air. In the absence of a stratum corneum, the slime coat serves to protect the fish from attack from harmful microorganisms.[13] This is chiefly done by sloughing off microbes which become trapped in the slime coat, but the slime coat contains antimicrobial peptides and other defensive properties such as lysozyme and C-reactive protein.[14]

Parrotfish create extra mucus during sleep which covers their bodies in a cocoon-like structure. It protects them from predators and parasites by masking their scent and providing a physical barrier against them.[15]

The slime of the hagfish is unique due to its volume and dilution. In these fish it serves as an anti-predator adaptation: when grabbed by a predator fish, the hagfish ejects copious amounts of slime into the predator's mouth, causing the predator to gag and flare its gills, releasing the hagfish and moving away.[16]

Human importance

In pisciculture and fishkeeping, the slime coat is important to the health of fish,[17] particularly during transport which can cause damage to it.[18] High ammonia levels in the water can also cause damage to the slime coat.[19]

The antimicrobial properties of fish slime have been studied as an alternative to antibiotic drugs to address antibiotic resistance.[20] [21]

See also

Further reading

Notes and References

  1. Jakowska. Sophie. 1963. Mucus Secretion in Fish—a Note*. Annals of the New York Academy of Sciences. en. 106. 2. 458–462. 10.1111/j.1749-6632.1963.tb16658.x. 13964523. 1963NYASA.106..458J. 13445731. 1749-6632.
  2. Web site: Kraugerud. Reidun Lilleholt. Fish skin and its protective properties. 2021-09-13. Nofima. 15 January 2021 . en-US.
  3. Rakers. Sebastian. Niklasson. Lars. Steinhagen. Dieter. Kruse. Charli. Schauber. Jürgen. Sundell. Kristina. Paus. Ralf. 2013. Antimicrobial Peptides (AMPs) from Fish Epidermis: Perspectives for Investigative Dermatology. Journal of Investigative Dermatology. 133. 5. 1140–1149. 10.1038/jid.2012.503. 23407389. 0022-202X. free.
  4. Tiralongo. Francesco. Messina. Giuseppina. Lombardo. Bianca Maria. Longhitano. Lucia. Li Volti. Giovanni. Tibullo. Daniele. 2020. Skin Mucus of Marine Fish as a Source for the Development of Antimicrobial Agents. Frontiers in Marine Science. 7. English. 10.3389/fmars.2020.541853. 2296-7745. free.
  5. Rosen. Moe Wm. Cornford. Neri E.. 1971. Fluid Friction of Fish Slimes. Nature. en. 234. 5323. 49–51. 10.1038/234049a0. 1971Natur.234...49R. 4268462. 1476-4687.
  6. Daniel. Thomas L.. 1981-06-01. Fish mucus: in situ measurements of polymer drag reduction. The Biological Bulletin. 160. 3. 376–382. 10.2307/1540846. 1540846. 0006-3185. Biodiversity Heritage Library.
  7. Web site: Slime Reduces Drag — Biological Strategy. 2021-09-12. asknature.org. en-US. Biomimicry Institute.
  8. Web site: Ramel. Gordon. 2020-03-24. Fish Locomotion & Movement 101: How Fish Swim Explained. 2021-09-12. Earth Life. en-US.
  9. Book: Blake, Robert W.. Fish Locomotion. 1983-05-26. CUP Archive. 978-0-521-24303-2. 66–68. en.
  10. Book: Domenici, Paolo. Fish Locomotion: An Eco-ethological Perspective. 2010-01-01. CRC Press. 978-1-000-73803-2. 100. en. 10.1086/656882.
  11. Braun. C.. Reef. R.. Siebeck. U. E.. 2016-07-01. Ultraviolet absorbing compounds provide a rapid response mechanism for UV protection in some reef fish. Journal of Photochemistry and Photobiology B: Biology. en. 160. 400–407. 10.1016/j.jphotobiol.2016.04.020. 27162066 . 1011-1344.
  12. Eckes. Maxi J.. Siebeck. Ulrike E.. Dove. Sophie. Grutter. Alexandra S.. 2008-01-17. Ultraviolet sunscreens in reef fish mucus. Marine Ecology Progress Series. en. 353. 203–211. 10.3354/meps07210. 2008MEPS..353..203E . 0171-8630. free.
  13. Tsutsui. Shigeyuki. Komatsu. Yukie. Sugiura. Takaya. Araki. Kyosuke. Nakamura. Osamu. 2011-11-01. A unique epidermal mucus lectin identified from catfish (Silurus asotus): first evidence of intelectin in fish skin slime. The Journal of Biochemistry. 150. 5. 501–514. 10.1093/jb/mvr085. 21757471. 0021-924X.
  14. Dash. S.. Das. S. K.. Samal. J.. Thatoi. H. N.. 2018. Epidermal mucus, a major determinant in fish health: a review. Iranian Journal of Veterinary Research. 19. 2. 72–81. 1728-1997. 6056142. 30046316.
  15. Web site: Mucous Cocoon Protects From Predators — Biological Strategy. 2021-09-28. asknature.org. en-US.
  16. Zintzen. Vincent. Roberts. Clive D.. Anderson. Marti J.. Stewart. Andrew L.. Struthers. Carl D.. Harvey. Euan S.. 2011-10-27. Hagfish predatory behaviour and slime defence mechanism. Scientific Reports. en. 1. 1. 131. 10.1038/srep00131. 22355648. 3216612. 2011NatSR...1E.131Z. 2045-2322.
  17. Web site: Green . Christopher . Haukenes . Alf . September 2015 . The Role of Stress in Fish Disease . TAMU.
  18. Harmon . Todd S. . March 2009 . Methods for reducing stressors and maintaining water quality associated with live fish transport in tanks: a review of the basics . Reviews in Aquaculture . en . 1 . 1 . 58–66 . 10.1111/j.1753-5131.2008.01003.x.
  19. Ogbonna F. . Joel . Chinomso A. . Amajuoyi . February 2010 . DETERMINATION OF THE CONCENTRATION OF AMMONIA THAT COULD HAVE LETHAL EFFECT ON FISH POND. ARPN Journal of Engineering and Applied Sciences . 5 . 2.
  20. Kuppulakshmi . C. . Prakash . M. . Gunasekaran . G. . Manimegalai . G. . Sarojini . S. . 2008 . Antibacterial properties of fish mucus from Channa punctatus and Cirrhinus mrigala . European Review for Medical and Pharmacological Sciences . 12 . 3 . 149–153 . 1128-3602 . 18700685.
  21. Hussain . Ahmed . Sachan . Shashwati Ghosh . 2023-03-20 . Fish Epidermal Mucus as a Source of Diverse Therapeutical Compounds . International Journal of Peptide Research and Therapeutics . en . 29 . 3 . 36 . 10.1007/s10989-023-10505-6 . 1573-3904 . 10026197 . 36968337.

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