''Glaucus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of small blue

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

s. They are aeolid

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

s,Bouchet, P.; Gofas, S. (2013)
''Glaucus'' Forster, 1777.
Accessed through: World Register of Marine Species on 2013-07-17 ranging in size from . They feed on colonial

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

ns such as

Portuguese man o' war The Portuguese man o' war (''Physalia physalis''), also known as the man-of-war, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or blue bottle, which is ...

s, blue buttons, and purple sails. They can produce painful and potentially dangerous stings when handled, as they store the

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...

ous nematocysts of their prey. ''Glaucus'' is the only genus in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Glaucidae. It includes five species.

Taxonomic history

The genus ''Glaucus'' was established by monotypy in 1777 by the British naturalist

Johann Reinhold Forster Johann Reinhold Forster (22 October 1729 – 9 December 1798) was a German Reformed (Calvinist) pastor and naturalist of partially Scottish descent who made contributions to the early ornithology of Europe and North America. He is best known ...

. He described specimens of ''

Glaucus atlanticus ''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 small, blue sea slug, a pelagic (open-ocean) aeolid nudibran ...

'' recovered during the

second voyage of James Cook The second voyage of James Cook, from 1772 to 1775, commissioned by the British government with advice from the Royal Society, was designed to circumnavigate the globe as far south as possible to finally determine whether there was any great so ...

aboard . The genus is named after the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

sea-god

Glaucus In Greek mythology, Glaucus (; grc, Γλαῦκος, Glaûkos, glimmering) was a Greek prophetic sea-god, born mortal and turned immortal upon eating a magical herb. It was believed that he came to the rescue of sailors and fishermen in storms ...

. In 1848, the German naturalist Johannes Gistel provided the substitute name ''Dadone'' for ''Glaucus''. But it is unnecessary and is now regarded as

invalid Invalid may refer to: * Patient, a sick person * one who is confined to home or bed because of illness, disability or injury (sometimes considered a politically incorrect term) * .invalid, a top-level Internet domain not intended for real use As t ...

.Bouchet, P. (2015)
''Dadone'' Gistel, 1848.
Accessed through: World Register of Marine Species on 2015-09-23 The family Glaucidae was established in 1827 by the British zoologist

John Edward Gray John Edward Gray, FRS (12 February 1800 – 7 March 1875) was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray (1766–1828). The same is used for ...

to contain the genus. A second species in the family was described by the Danish

malacologist Malacology is the branch of invertebrate zoology that deals with the study of the Mollusca (mollusks or molluscs), the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, ...

Rudolph Bergh Rudolph Bergh (15 October 1824 – 20 July 1909), full name Ludvig Sophus Rudolph Bergh, was a Danish physician and malacologist. He worked in Copenhagen. As a doctor his speciality was sexually transmitted diseases. In Copenhagen a hospital an ...

in 1860. He placed it under a new genus ''Glaucilla''. However, the synapomorphies between ''Glaucus'' and ''Glaucilla'' have made the maintenance of both genera irrelevant. Therefore ''Glaucus'' is now regarded as the only genus within the family Glaucidae. Glaucidae is classified under the superfamily

Aeolidioidea Aeolidioidea is a superfamily of sea slugs, the aeolid nudibranchs. They are marine gastropod molluscs in the suborder Cladobranchia. Taxonomy As of 2019, the superfamily Aeolidioidea consisted of the following families: * Aeolidiidae Gray, ...

.Bouchet, P. (2013). Glaucidae. Accessed through:

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialis ...

Glaucidae Gray, 1827''Glaucus'' Forster, 1777
on 2014-06-11 In 2014, a careful DNA and anatomical study of the genus unexpectedly revealed the presence of a

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. Only one species was found in the Atlantic, but the name ''

Glaucus marginatus ''Glaucus marginatus'' is a species of small, floating, blue sea slug; a pelagic (open-ocean) aeolid nudibranch; a marine opisthobranch gastropod mollusc in the family Glaucidae.Valdés A. & Campillo O.A. (2004) ''Systematics of pelagic aeo ...

'' was revealed to include four separate species (referred to informally as the 'marginatus' clade). There are three species in the North Pacific Subtropical Gyre System and another species in the South Pacific Subtropical Gyre System. ''

'' also occurs throughout the Indo-Pacific as well as in the Atlantic Ocean. In the North Pacific are ''

'', '' Glaucus thompsoni'' and '' Glaucus mcfarlanei'', with ''Glaucus marginatus'' also occurring in the Indian Ocean and the South Pacific. Also in the South Pacific is '' Glaucus bennettae''. ''Glaucus atlanticus'' has some genetic differences in different parts of its range but is considered to be a single species.

Species

Species within the genus ''Glaucus'' include: * ''

'' Forster, 1777 –

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

* '' Glaucus bennettae'' Churchill, Valdés & Ó Foighil, 2014 – South Pacific * '' Glaucus mcfarlanei'' Churchill, Valdés & Ó Foighil, 2014 –

North Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

* ''

'' (Bergh, 1860) – Indo-Pacific * '' Glaucus thompsoni'' Churchill, Valdés & Ó Foighil, 2014 –

;Species brought into synonymy: * ''Glaucus distichoicus'' d'Orbigny, 1837: synonym of ''

'' Forster, 1777 * ''Glaucus flagellum'' Blumenblach, 1803: synonym of ''

'' Forster, 1777 * ''Glaucus hexapterigius'' Cuvier, 1805: synonym of ''

'' Forster, 1777 * ''Glaucus lineatus'' Reinhardt & Bergh, 1864: synonym of ''

'' Forster, 1777 * ''Glaucus longicirrhus'' Reinhardt & Bergh, 1864: synonym of ''

'' Forster, 1777

References

{{Use dmy dates, date=May 2017 Glaucidae Gastropod genera Taxa named by Johann Reinhold Forster