dcsimg
Image of Blue glaucus
Living things » » Animals » » Molluscs » Snails and slugs » » Glaucidae »

Blue Glaucus

Glaucus atlanticus Forster 1777

General Description

provided by EOL authors
The blue glaucus (Glaucus atlanticus), sometimes called the blue sea slug(1) or blue ocean slug,(2) is a bizarre-looking marine creature in the group of sea slugs known as nudibranchs.(2,3) Found in the temperate and tropical waters of the Pacific, Atlantic, and Indian Oceans,(2,3,4,5) this slender,(5) up-to-3-centimeter-long(3,5,6) slug lives its life floating upside-down on the surface of the ocean thanks to an air bubble which it swallows and keeps inside its stomach.(1,2,4,5) Its color pattern, an example of a phenomenon known as countershading,(2) helps it avoid both flying and swimming predators while floating wherever the wind and the currents take it(4): its underside, which faces upward, is blue, helping it blend into the water’s surface when seen from above, while its back, which faces downward, is a more grayish color, helping it blend into the ocean when seen from below.(2,3) This camouflage, however, is not the blue glaucus’ only form of self-defense. It feeds on animals known as hydrozoans (in the same phylum as jellyfish), especially the highly venomous Portuguese Man-O’-War.(1,2,3,4) Although a sting by a Portuguese Man-O’-War is very painful to a human,(4) the blue glaucus, like some other nudibranchs, can swallow its prey’s stinging cells (known as nematocysts) without hurting itself.(1,2,7,8) It may be able to protect itself from the sting both by secreting mucus and by hard discs in its skin.(7,8) Far from being harmed by the poison, the blue glaucus stores it in the up to 84 finger-like structures or cerata(3,6) sticking out of its body, and uses it to defend itself against predators.(1,2,3,4,6)
license
cc-by-3.0
copyright
Noah Weisz
partner site
EOL authors

Overview

provided by EOL authors
If you heard about a tiny, funny-looking animal that spends its life floating upside-down on the surface (1,2,3) of the Pacific, Atlantic, or Indian Ocean(2,3,4,5) thanks to an air bubble which it swallows and keeps inside its belly,(1,2,3,5) going wherever the currents and the wind take it,(3) you would probably think it was just a harmless creature that likes to relax in the water. But this slender,(5) up-to-3-centimeter-long(4,5,6) animal, which is called the blue glaucus,(3) blue sea slug,(1) or blue ocean slug,(2) is not nearly as innocent as it seems. The first trick it’s got up its sleeve is a form of camouflage called countershading that protects it from both flying and swimming predators while it floats.(2) The underside of the blue glaucus, which faces upward, is blue, helping it blend into the water’s surface when seen from above, while its back, which faces downward, is a more grayish color, helping it blend into the ocean when seen from below.(2,4) The second tricky feature of the blue glaucus is even more amazing. It feeds on hydrozoans (a group of animals in the same phylum as jellyfish), especially the highly poisonous Portuguese Man-O’-War.(1,2,3,4) Although a sting by a Portuguese Man-O’-War is very painful to a human,(3) the blue glaucus, like some other sea slugs, can swallow its prey’s stinging cells (known as nematocysts) without hurting itself.(1,2,7,8) It may keep itself safe from the poison by releasing protective mucus and by hard barrier-like discs inside its skin.(7,8) But the blue glaucus does more than simply protect itself against these stings. It stores the swallowed poison inside the up to 84 finger-like structures or cerata(4,6) sticking out of its body, and then uses this poison to defend itself against other predators!(1,2,3,4,6)
license
cc-by-3.0
copyright
Noah Weisz
partner site
EOL authors

Glaucus atlanticus

provided by wikipedia EN

Glaucus atlanticus (common names include the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug) is a species of small, blue sea slug, a pelagic aeolid nudibranch, a shell-less gastropod mollusk in the family Glaucidae.[2]

These sea slugs are pelagic: they float upside down by using the surface tension of the water to stay up, where they are carried along by the winds and ocean currents. Glaucus atlanticus makes use of countershading: the blue side of their body faces upwards, blending in with the blue of the water. The silver/grey side of the sea slugs faces downwards, blending in with the sunlight reflecting on the ocean's surface when viewed upwards underwater.

Glaucus atlanticus feed 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, Glaucus marginatus, which is now understood to be not one species, but a cryptic species complex of four separate species that live in the Indian Ocean and Pacific Ocean.[1][3] It shares the common name "Blue Dragon" with Pteraeolidia ianthina.

Description

At maturity Glaucus atlanticus can be up to 3 centimetres (1.2 in) in length.[4] 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.[5]

Cerata, also known as papillae, extend laterally from three different pairs of peduncles. The papillae is placed in a single row (uniseriate) and may be up to 84 inches total, (Forster, 1777). [6]

The radula of this species bears serrated teeth.[7]

Buoyancy and coloration

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 snail), 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.[8] The blue coloration is also thought to reflect harmful UV sunlight.

Distribution and habitat

"
The blue sea slug is shown here out of water, and thus collapsed; these were found on a beach. Picking up the animal 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 there is some evidence 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] The G. atlanticus species geographical range increased northward by 150 km in the Gulf of California.[9]

Glaucus atlanticus was recently found in the Humboldt Current ecosystem in Peru in 2013, and off Andhra Pradesh in India in 2012. This is in line with the known habitat characteristics of the species: they live in warm temperate climates in the Southern Pacific, and in circumtropical and Lusitanian environments. Before finding Glaucus 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 kilometers apart.[10] Glaucus atlanticus was also recently found off Bermuda in January 2016.[11]

Although these sea slugs live on the open ocean, they sometimes accidentally wash up onto the shore, and therefore they may be found on beaches.[12]

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 to make slow swimming movements.[13] [14] 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.

G. atlanticus is able to feed on the Portuguese man o' war due to its immunity to the venomous nematocysts. The slug consumes the entire organism and appears to select and store the most venomous nematocysts for its own use. The nematocysts are collected in specialized sacs (cnidosacs) at the tip of the animal's cerata, the thin feather-like "fingers" on its body. Because Glaucus concentrates the venom, it can produce a more powerful and deadly sting than the Man o' War on which it feeds.[15]

Like almost all heterobranchs, Glaucus is a hermaphrodite, having both male and female reproductive organs. Unlike most nudibranchs, which mate with their right sides facing, sea swallows mate with ventral sides facing.[16] After mating, both animals produce egg strings. Studies have indicated that the 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.[17]

Sting

The Glaucus atlanticus is able to swallow the venomous nematocysts from siphonophores such as the Portuguese man o' war, and store them in the extremities of its finger-like cerata.[15] Picking up the animal can result in a painful sting, with symptoms similar to those caused by the Portuguese man o' war.[18] The symptoms that may appear after being stung are nausea, pain, vomiting, acute allergic contact dermatitis, erythema, urticarial papules, potential vesicle formation and post-inflammatory hyperpigmentation.[19]

References

  1. ^ a b "Glaucus". WoRMS. World Register of Marine Species. Retrieved 5 August 2012.
  2. ^ Lalli, C. M.; Gilmer, R. W. (1989). Pelagic snails: the biology of holoplanktonic gastropod mollusks. Stanford University Press. p. 224. ISBN 978-0-8047-1490-7. Retrieved 13 January 2010.
  3. ^ a b Churchill, Celia K. C.; Valdés, Ángel; ó Foighil, Diarmaid (2014). "Churchill, C. K. C.; Valdés, Á; Ó Foighil, D. (2014). Molecular and morphological systematics of neustonic nudibranchs (Mollusca : Gastropoda : Glaucidae : Glaucus), with descriptions of three new cryptic species. Invertebrate Systematics. 28(2): 174-195". Invertebrate Systematics. 28 (2): 174. doi:10.1071/IS13038.
  4. ^ "Glaucus atlanticus (blue sea slug)". The Natural History Museum. Archived from the original on 27 June 2015. Retrieved 13 April 2013.
  5. ^ Piper, R. (2007). Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Greenwood Publishing Group. pp. 42–43. ISBN 978-0-313-33922-6.
  6. ^ Holland, Brenden (March 2012). "First record of the blue sea slug (Glaucus atlanticus) from Andhra Pradesh – India" (PDF). Semantic Scholar.
  7. ^ Thompson, T. E.; McFarlane, I. D. (2008). "Observations on a collection of Glaucus from the Gulf of Aden with a critical review of published records of Glaucidae (Gastropoda, Opisthobranchia)". Proceedings of the Linnean Society of London. 178 (2): 107–123. doi:10.1111/j.1095-8312.1967.tb00967.x.
  8. ^ "Habitat - Glaucus Atlanticus". Bluedragonslug.weebly.com. Retrieved 14 March 2018.
  9. ^ Hernández, Luis, et al. “Occurrence of Glaucus Atlanticus in the Midriff Islands Region, Gulf of California, Mexico.” American Malacological Bulletin, vol. 36, no. 1, 2018, pp. 145–149.
  10. ^ 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" (341–8391): 43–60. Retrieved 24 October 2014. Cite journal requires |journal= (help)
  11. ^ Johnston-Barnes, Owain (25 January 2016). "Diver finds 'blue dragons' at Spittal Pond". The Royal Gazette.
  12. ^ Taprobanica. Taprobanica Private Limited. April 2012. pp. 52–53. Retrieved 24 October 2014.
  13. ^ Srinivasulu, Bhargavi, C. Srinivasulu, and G. Chethan Kumar. "First record of the blue sea slug (Glaucus atlanticus) from Andhra Pradesh–India." Taprobanica: The Journal of Asian Biodiversity 4.1 (2012): 52-53.
  14. ^ MacLellan, Amelia "Glaucus atlanticus (blue sea slug)". The Natural History Museum. Retrieved 2013-04-13
  15. ^ a b Rudman, W. B. (6 November 1998). "Glaucus atlanticus Forster, 1777". Sea Slug Forum. Retrieved 26 February 2011.
  16. ^ Debelius, H.; Kuiter, R. H. (2007). Nudibranchs of the world. IKAN-Unterwasserarchiv. ISBN 978-3-939767-06-0.
  17. ^ Churchill, Celia K. C.; Valdés, Ángel; Ó Foighil, Diarmaid (1 April 2014). "Afro-Eurasia and the Americas present barriers to gene flow for the cosmopolitan neustonic nudibranch Glaucus atlanticus". Marine Biology. 161 (4): 899–910. doi:10.1007/s00227-014-2389-7. ISSN 1432-1793.
  18. ^ Ottuso, Patrick Thomas (May 2009). "Aquatic antagonists: Indirect nematocyst envenomation and acute allergic contact dermatitis due to nudibranchs" (PDF). Cutis. 83.
  19. ^ Pinotti, Raphael M.; Bom, Fabio C.; Muxagata, Erik; Pinotti, Raphael M.; Bom, Fabio C.; Muxagata, Erik (2019). "On the occurrence and ecology of Glaucus atlanticus Forster, 1777 (Mollusca: Nudibranchia) along the Southwestern Atlantic coast". Anais da Academia Brasileira de Ciências. 91 (1). doi:10.1590/0001-3765201920180154. ISSN 0001-3765.
license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Glaucus atlanticus: Brief Summary

provided by wikipedia EN

Glaucus atlanticus (common names include the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug) is a species of small, blue sea slug, a pelagic aeolid nudibranch, a shell-less gastropod mollusk in the family Glaucidae.

These sea slugs are pelagic: they float upside down by using the surface tension of the water to stay up, where they are carried along by the winds and ocean currents. Glaucus atlanticus makes use of countershading: the blue side of their body faces upwards, blending in with the blue of the water. The silver/grey side of the sea slugs faces downwards, blending in with the sunlight reflecting on the ocean's surface when viewed upwards underwater.

Glaucus atlanticus feed 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.

license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Description

provided by World Register of Marine Species
A distinctive, truly pelagic silvery blue mollusc, up to 6 cm long, with three pairs of arms. Floats upside-down just under the sea surface, feeding on the colonial hydroids Physalia, Porpita and Velella. Habitat: offshore. Distribution: pantropical. N.B. must be handled with care as it can give an extremely painful sting, due to the nematocysts taken from the prey species Physalia, which itself gives a nasty sting.
license
cc-by-4.0
copyright
WoRMS Editorial Board
bibliographic citation
Richmond, M. (Ed.) (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean islands. Sida/Department for Research Cooperation, SAREC: Stockholm, Sweden. ISBN 91-630-4594-X. 448 pp.
i18n: Contributor
Edward Vanden Berghe [email]