Glaucus atlanticus

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Glaucus atlanticus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Order: Nudibranchia
Suborder: Cladobranchia
Family: Glaucidae
Genus: Glaucus
Species:
G. atlanticus
Binomial name
Glaucus atlanticus
Forster, 1777
Synonyms[1]
  • Doris radiata Gmelin, 1791 (synonym)
  • Glaucus distichoicus d'Orbigny, 1837
  • Glaucus flagellum Blumenblach, 1803 (synonym)
  • Glaucus hexapterigius Cuvier, 1805 (synonym)
  • Glaucus lineatus Reinhardt & Bergh, 1864
  • Glaucus longicirrhus Reinhardt & Bergh, 1864

Glaucus atlanticus (common names include the blue sea dragon, sea swallow, blue angel, blue glaucus, dragon slug, blue dragon, blue sea slug, and blue ocean slug) is a species of sea slug in the genus Glaucus.[2]

These sea slugs live in the pelagic zone (open ocean), where they float upside-down by using the surface tension of the water to stay afloat. They are carried along by the winds and ocean currents. G. atlanticus makes use of countershading; the blue side of their bodies faces upwards, blending in with the blue of the water. The silver/grey side of the sea slug faces downwards, blending in with the sunlight reflecting on the ocean's surface when viewed from below the surface of the water.

G. atlanticus feeds on other pelagic creatures, including the Portuguese man o' war and other venomous siphonophores. This sea slug stores stinging nematocysts from the siphonophores within its own tissues as defence against predators. Humans handling the slug may receive a very painful and potentially dangerous sting.

Taxonomy

This species looks similar to, and is closely related to,

cryptic species complex of four separate species that live in the Indian and Pacific Oceans.[1][3] It shares the common name "blue dragon" with Pteraeolidia ianthina[4] and G. marginatus.[5]

Description

At maturity, G. atlanticus is usually around 3 cm (1.2 in) in length,[6] though larger specimens have been found.[7] It can live up to a year under the right conditions.[8] It is silvery grey on its dorsal side and dark and pale blue ventrally. It has dark blue stripes on its head. It has a flat, tapering body and six appendages that branch out into rayed, finger-like cerata.[9]

Cerata, also known as papillae, extend laterally from three different pairs of peduncles. The papillae are placed in a single row (uniseriate) and may be up to 84 inches total (Forster, 1777).[10]

G. atlanticus is usually found in tropical/subtropical areas, floating at the ocean's surface due to the stored gulped air inside its stomach. It usually feeds on cnidarians, which can be noisy due to air escaping its stomach as it feeds.[11][12][13]

The radula of this species bears serrated teeth,[14] which paired with a strong jaw and denticles, allows it to grasp and "chip down" parts of its prey.[8]

Buoyancy and coloration

See also: Ocean surface ecosystem

With the aid of a gas-filled sac in its stomach, G. atlanticus floats at the surface. Due to the location of the gas sac, this species floats upside down. The upper surface is actually the foot (the underside in other slugs and snails), and this has either a blue or blue-white coloration. The true

dorsal surface (carried downwards in G. atlanticus) is completely silver-grey. This coloration is an example of countershading, which helps protect it from predators that might attack from below and from above.[15] The blue coloration is also thought to reflect harmful ultraviolet
sunlight.

Distribution and habitat

Glaucus atlanticus is the blue sea slug shown here out of water on a beach, and thus collapsed; however, touching the animal directly with your skin can result in a painful sting, with symptoms similar to those caused by the Portuguese man o' war
The slug in the water

This nudibranch is pelagic, and some evidence indicates that it occurs throughout the world's oceans, in temperate and tropical waters. It has been recorded from the east and south coasts of South Africa, European waters, the east coast of Australia, and Mozambique.[3] Observations in 2015 and 2016 suggested that the G. atlanticus species' geographical range had increased northward by 150 km in the Gulf of California compared with previous sightings.[16]

Since the middle of the 19th century, records of this species have been reported on the Azores.[7]

G. atlanticus was recently found in the

Lusitanian environments. Before finding G. atlanticus off Andhra Pradesh, these nudibranchs were documented as having been seen in the Bay of Bengal and off the coast of Tamil Nadu, India, over 677 km apart.[17] G. atlanticus was also recently found off Bermuda in January 2016,[18]
and uncommonly washes ashore on east coast beaches at Barbados, Lesser Antilles.

Although these sea slugs live on the open ocean, they sometimes accidentally wash up onto the shore, so they may be found on beaches.[19] In April 2022, specimens were found in the Gulf of Mexico along the Texas coast.[20] On August 31, 2023, blue sea slugs were reported to be found along Karon Beach, Phuket, Thailand.[21][22]

Life history and behavior

G. atlanticus preys on other larger pelagic organisms. The sea slugs can move toward prey or mates by using their cerata, the thin feather-like "fingers" on its body, to make slow swimming movements.[23][24] They are known to prey on the dangerously venomous Portuguese man o' war (Physalia physalis), the by-the-wind-sailor (Velella velella), the blue button (Porpita porpita), and the violet snail, Janthina janthina. Occasionally, individuals attack and eat other individuals in captivity.

The species is able to feed on the Portuguese man o' war due to its immunity to the venomous

nematocysts. The slug consumes chunks of the organism and appears to select and store the most venomous nematocysts for its own use against future prey.[25] The nematocysts are collected in specialized sacs (cnidosacs) at the tip of the animal's cerata. Because G. atlanticus concentrates the venom, it can produce a more powerful and deadly sting than the man o' war on which it feeds.[26]

Like almost all

hermaphrodites and their male reproductive organs have evolved to be especially large and hooked to avoid their partner's venomous cerata.[8] Unlike most nudibranchs, which mate with their right sides facing, sea swallows mate with ventral sides facing.[27] After mating, both individuals are able to lay eggs and can release up to 20 on an egg string, often laying them in wood pieces or carcasses.[8] On average, G. atlanticus can lay 55 egg strings per hour.[28] G. atlanticus is not globally panmictic, but is localized within ocean basins. Gene flow among Afro-Eurasian and American populations is thus hindered by physical obstructions and water temperatures in the Arctic and Southern Oceans.[29]

Sting

G. atlanticus is able to swallow the venomous nematocysts from

vesicle formation and postinflammatory hyperpigmentation.[31]

References

  1. ^ a b "Glaucus". WoRMS. World Register of Marine Species. Retrieved 5 August 2012.
  2. ISBN 978-0-8047-1490-7
    .
  3. ^
    S2CID 84010907
    .
  4. ^ Rudman, W. B. (15 July 2010). "Pteraeolidia ianthina (Angas,1864)". The Sea Slug Forum. Australian Museum. Retrieved 13 February 2021.
  5. ^ Salleh, Anna (12 February 2021). "Bizarre 'blue fleet' blows onto Australia's east coast". ABC News. Australian Broadcasting Corporation. Retrieved 13 February 2021.
  6. ^ "Glaucus atlanticus (blue sea slug)". The Natural History Museum. Archived from the original on 27 June 2015. Retrieved 13 April 2013.
  7. ^ a b "Dragão Azul do Mar". RTP. Retrieved 14 November 2020.
  8. ^
    Smithsonian Museum of Natural History
    . Retrieved 14 November 2020.
  9. ISBN 978-0-313-33922-6
    .
  10. S2CID 130162921
    .
  11. S2CID 253737326
    .
  12. S2CID 245186096
    .
  13. S2CID 119501907
    .
  14. doi:10.1111/j.1095-8312.1967.tb00967.x
    .
  15. ^ "Habitat – Glaucus Atlanticus". Bluedragonslug.weebly.com. Retrieved 14 March 2018.
  16. S2CID 89794645
    .
  17. ^ Uribe, Roberto A.; Nakamura, Katia; Indacochea, Aldo; Pacheco, Aldo S.; Hooker, Yuri; Schrödl, Michael (September 2013). "A review on the diversity and distribution of opisthobranch gastropods from Peru, with the addition of three new records". Spixiana. 36 (341–8391): 43–60. Retrieved 24 October 2014.
  18. ^ Johnston-Barnes, Owain (25 January 2016). "Diver finds 'blue dragons' at Spittal Pond". The Royal Gazette.
  19. ^ Taprobanica. Taprobanica Private Limited. April 2012. pp. 52–53. Retrieved 24 October 2014. [dead link]
  20. ^ Patton, Mary Claire (11 April 2022). "Don't Touch: Rare blue dragons are showing up on Texas beaches again". KSAT 12.
  21. ^ "Venomous 'blue dragon' found on Phuket beach". Bangkok Post. Retrieved 1 September 2023.
  22. ^ Petpailin, Petch (31 August 2023). "Beach warning: Venomous blue dragon sea slug spotted in Phuket". Thaiger. Retrieved 1 September 2023.
  23. doi:10.4038/tapro.v4i1.4386
    .
  24. ^ MacLellan, Amelia "Glaucus atlanticus (blue sea slug)". The Natural History Museum. Retrieved 2013-04-13
  25. ^ Asmelash, Leah (9 May 2020). "Rare blue dragons are washing up on the Padre Island National Seashore". CNN. Retrieved 11 May 2020.
  26. ^
    Rudman, W. B. (6 November 1998). "Glaucus atlanticus Forster, 1777"
    . Sea Slug Forum. Retrieved 26 February 2011.
  27. ISBN 978-3-939767-06-0
    .
  28. S2CID 245186096
    .
  29. S2CID 84153330
    .
  30. ^ Ottuso, Patrick Thomas (May 2009). "Aquatic antagonists: Indirect nematocyst envenomation and acute allergic contact dermatitis due to nudibranchs" (PDF). Cutis. Vol. 83. Archived from the original (PDF) on 23 July 2021. Retrieved 27 April 2015.
  31. PMID 30994760
    .

Further reading

External links

Wikimedia Commons has media related to Glaucus atlanticus.
Wikispecies has information related to Glaucidae.
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