''Glaucus marginatus'' is a species of small, floating, blue

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 t ...

; a

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 wa ...

(open-ocean) aeolid nudibranch; a marine

opisthobranch Opisthobranchs () is now an informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping. Euopisth ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc in the family

Glaucidae ''Glaucus'' is a genus of small blue pelagic sea slugs. They are aeolid nudibranchs,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 colon ...

.Valdés A. & Campillo O.A. (2004) ''Systematics of pelagic aeolid nudibranchs of the family Glaucidae (Mollusca, Gastropoda)''. Bulletin of Marine Science 75(3): 381–38

/ref> This species is closely related to ''

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 ...

'', and is part 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 ...

(Informal clade Marginatus) along with '' Glaucus bennettae'', '' Glaucus thompsoni'', and '' Glaucus mcfarlanei''.Churchill C.K.C, Valdés A. & 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): 174-19

/ref> Like ''Glaucus atlanticus'', it is commonly known as a blue dragon.

Description

This nudibranch is dark blue, and in many ways it resembles a smaller version of ''Glaucus atlanticus''. However, in this species the

cerata :''The tortrix moth genus ''Cerata'' is considered a junior synonym of ''Cydia. Cerata, singular ceras, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine opisthobranch gastropod mollusks ...

are arranged in a single row in each arch. While ''G. atlanticus'' is up to long, ''G. marginate'' is only about long, and its tail is shorter than its cousin. The species has a light and dark blue foot.

Distribution

This species is

, and can be found in the

Pacific Ocean 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 ...

. While they do not usually inhabit coastal regions, hundreds of the creatures were observed washing up on one of the Sydney North Shore beaches, near Long Reef, in February 2021.

Habitat and behaviour

These small nudibranches float upside down on the

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to f ...

in temperate and tropical seas. They eat 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 th ...

ns such as the

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 ...

(aka bluebottle, or ''Physalia utriculus''),

blue button The Blue Button is a system for patients to view online and download their own personal health records. Several Federal agencies, including the Departments of Defense, Health and Human Services, and Veterans Affairs, implemented this capabili ...

s (''Porpita porpita''), and the

by-the-wind sailor ''Velella'' is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is ''Velella velella'', a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raf ...

(''Velella velella'').

References

Sources

* Bergh, L.S.R. (1860). ''Om Forekomsten af Neldefiim hos Mollusker''. Vidensk. Meddel. Naturh. Foren. Kjöbenhavn, p. 309-331, pl. 8.
Burn R. (2006) ''A checklist and bibliography of the Opisthobranchia (Mollusca: Gastropoda) of Victoria and the Bass Strait area, south-eastern Australia''. Museum Victoria Science Reports 10:1–42
*
Australian Museum Online sections - sea slug forums

External links

{{Taxonbar, from=Q3003897 Glaucidae Gastropods described in 1864