AnimalTracks.wiki

What the sources say

Blue Sea DragonGlaucus atlanticus

Every figure, record and mechanism on the Blue Sea Dragon profile was written from a source, and this is the working table behind it: 39 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

Profile updated

Source
01

Oceana

Blue Glaucus. Oceana.

The page saysAir-bubble buoyancy
The source saysstaying afloat by storing air bubbles in their stomach
The page saysNot Evaluated
The source sayslittle is known about its conservation statusNote: GBIF's copy of the Red List returns NOT_EVALUATED for Glaucus atlanticus Forster, 1777, usage key 5190072 (https://api.gbif.org/v1/species/5190072/iucnRedListCategory), checked 2026-09-13, and neither the prefetch nor Crossref has an assessment DOI. GBIF is recorded here rather than cited, because its API returns bare JSON with no page a reader can open (the man o' war and alpaca followed the same pattern).
The page saysis a nudibranch, a shell-less sea slug
The source saysthis tiny sea slug ... the blue glaucus is a species of nudibranch, a group of soft-bodied, shell-less marine gastropods
The page saysa slug that floats upside down at the surface
The source saysthey spend most of their lives floating upside-down at the surface

Source
02

Bureau of Ocean Energy Management, U.S. Department of the Interior 2024

Blue Dragon Sea Slug. Bureau of Ocean Energy Management, U.S. Department of the Interior, 2024.

The page saysSurface of the open ocean
The source saysEcosystem: Surface of the open ocean
The page sayssteals a Portuguese man o' war's stinging cells and stores them in its own cerata
The source saysvenomous creatures such as Portuguese Man O’ War ... Glaucus atlanticus appropriates the victim’s stinging cells and stores them in its cerata
The page saysabout 3 centimeters long, barely over an inch
The source saysapproximately 3 cm (1.2 in) in sizeNote: Oceana gives 'about 2.5 centimeters (1 inch)'; the dated 2024 BOEM page is used
The page saysIt spends its life drifting at the surface of the open ocean
The source saysEcosystem: Surface of the open ocean ... is an ocean drifter, spending its life carried by ocean currents and the wind
The page saystendril-tipped appendages called cerata that spread like wings
The source saysit has three pairs of tendril-tipped appendages that spread like wings, getting shorter as they go down its body
The page saysA borrowed sting, concentrated
The source saysappropriates the victim’s stinging cells and stores them in its cerata in a more highly concentrated dosage
The page saysThe blue sea dragon stores the stinging cells it steals in its cerata in a more highly concentrated dose, which gives an animal about 3 centimeters long a vicious sting
The source saysappropriates the victim’s stinging cells and stores them in its cerata in a more highly concentrated dosage. At approximately 3 cm (1.2 in) in size, this increase potency of venom gives the blue dragon a vicious stingNote: replaces the 1998 Sea Slug Forum 'much more deadly' comparison, which the 2019 paper ('as harmful to humans as their prey') contradicts
The page saysBlue sea dragons sometimes wash ashore, and an encounter with even a dead one can result in getting stung
The source saysThe group’s greater mass can sometimes cause them to be washed ashore by oceanic winds and tide. But beachcombers need to careful if they come across them, because an encounter with even a dead blue dragon sea slug can result in getting stung
The page saysIt lives in tropical and temperate waters of the Atlantic, Pacific and Indian oceans
The source saysTropical and temperate waters of the Atlantic, Pacific, and Indian OceansNote: BOEM's Distribution line (release date 03/19/2024).

Source
03

Rudman, W.B. 1998

Rudman, W.B. (1998). Glaucus atlanticus Forster, 1777. Sea Slug Forum, Australian Museum.

The page saysblue-and-silver countershading
The source saysThey both exhibit a textbook example of colour countershading... is blue or blue and white... Their true dorsal surface, which faces down in the water, is silvery grey
The page saystropical and temperate waters circling the globe
The source saysCircumglobal in temperate and tropical waters.Note: 'circling the globe' for 'circumglobal'
The page saysAlong with the rest of the "blue fleet" of surface-dwelling animals it drifts among, it is carried by the currents and the winds
The source sayslive in close association with what Sir Alistair Hardy described ... The Blue Fleet ... All these animals float on the surface of the ocean being carried by the currents and the winds.
The page saysBecause it floats upside down, its foot faces the sky, and its colors are a textbook example of countershading
The source saysThey both exhibit a textbook example of colour countershading. Their foot and undersides of the cerata, (which because they float upside down is effectively their dorsal surface)
The page saysThe foot is blue, which helps camouflage it from seabirds hunting above
The source saysTheir foot and undersides of the cerata, ... is blue or blue and white which helps to camouflage them from predation (sea birds) from above
The page saysIts true back faces down and is silvery grey, camouflaging it from fish looking up from below
The source saysTheir true dorsal surface, which faces down in the water, is silvery grey to effectively camouflage them from fish looking up from below.
The page saysIt also appears to select the man o' war's most venomous stinging cells to store
The source saysit appears that they are able to select the most venomous of Physalia's stinging nematocysts for their own use
The page saysIt floats upside down at the surface, partly buoyed by a gas bubble in its stomach. Its blue side faces up and helps camouflage it from seabirds above, and its silvery-grey back faces down to camouflage it from fish looking up from below.
The source saysAll these animals float on the surface of the ocean ... Both species spend their life floating upside down in the water, partially bouyed by a gas bubble in their stomachs. ... Their foot and undersides of the cerata, (which because they float upside down is effectively their dorsal surface), is blue or blue and white which helps to camouflage them from predation (sea birds) from above. Their true dorsal surface, which faces down in the water, is silvery grey to effectively camouflage them from fish looking up from below.
The page sayscarried by the currents and the winds
The source saysAll these animals float on the surface of the ocean being carried by the currents and the winds.

Source
04

Yamamoto, Kanai, Miura & Oguchi 2025

Yamamoto, Kanai, Miura & Oguchi (2025). Blue angels have devil hands: Predatory behavior using cerata in Glaucus atlanticus. Ecology.

The page saysKleptocnidae
The source saysGlaucus species engage in kleptocnidae, recycling nematocysts from cnidarians
The page sayskept afloat partly by air bubbles in its stomach
The source saysall species of Glaucus are pleuston ... species that live on the ocean's surface, using cerata and air bubbles in their stomach cavities for buoyancyNote: 'partly' because the cerata also give buoyancy
The page saysDown each side of its body
The source saysall species of the genus Glaucus ... on each side of their bodies
The page saysScientists long thought cerata were mainly for defense
The source saysIt has long been postulated that kleptocnidae and cerata in Cladobranchia are mainly defensive organs
The page saysA 2025 study that reared the slugs in aquaria filmed something else
The source saysIssue date 2025 Mar. ... we report that Glaucus atlanticus successfully reared in aquaria employ their cerata for prey captureNote: 'filmed' rests on the paper's video supplements: 'the basal portion of the anteriormost cerata was observed to move flexibly to grasp the prey (Figure 1f,g ; see Video_S4.mov, Video_S5.mov, Video_S6.mov, Video_S7.mov in Oguchi, 2024 )'.
The page saysSome used their front-most cerata as hands to catch live whitebait, holding the fish between them while biting near its gills, and used the same "hands" on jellyfish
The source saysWhen some specimens of G. atlanticus were reared with live whitebait ... they surprisingly employed the most anterior cerata as “hands” to capture whitebait ... held the whitebait between the cerata and began biting near the gills ... G. atlanticus preyed on all tested cnidarian jellyfish ... The predatory use of the most anterior cerata as “hands” was also observed during cnidarian predation
The page saysThe base of those front cerata is longer than the rest and may work like an arm: researchers watched it move flexibly to grasp prey
The source saysthe basal part of the anteriormost cerata is longer than that of the other cerata and may function like an arm ... the basal portion of the anteriormost cerata was observed to move flexibly to grasp the prey
The page saysIt eats stinging animals that float at the surface, and the stinging cells it swallows travel through its gut into special cells called cnidophages, inside pouches called cnidosacs at the tips of its cerata. Scientists call the trick kleptocnidae: stealing someone else's weapons instead of making your own.
The source saysNematocysts are a type of organelle unique to cnidarians ... store nematocysts in the distal part of each ceras in an organ called the “cnidosac,” ... During the process of incorporating the ingested nematocysts, they are transported through the digestive tract into specialized cells called “cnidophages” located in the cnidosac ... prey on other pleustonic cnidarian species ... Glaucus species engage in kleptocnidae, recycling nematocysts from cnidarians

Source
05

Pinotti, Bom & Muxagata 2019

Pinotti, Bom & Muxagata (2019). On the occurrence and ecology of Glaucus atlanticus Forster, 1777 (Mollusca: Nudibranchia) along the Southwestern Atlantic coast. Anais da Academia Brasileira de Ciências.

The page saysa sting borrowed from the Portuguese man o' war
The source saysGlaucus species use the ingestion of both fired and undischarged nematocysts of their prey as a defensive strategy, concentrating them inside cnidosacs located at the tip of each cerata ... Along the Southwestern Atlantic Ocean, G. atlanticus mainly feed on V. velella , P. porpita and P. physalis cnidarians
The page saysPortuguese man o' war, blue buttons (Porpita), and by-the-wind sailors (Velella)
The source saysthe by-the-wind sailor Velella velella (Linnaeus, 1758), the blue-button Porpita porpita (Linnaeus, 1758) and the Portuguese man-o'-war Physalia physalis (Linnaeus, 1758)
The page saysThe blue sea dragon usually preys on stinging animals that drift at the surface, such as the Portuguese man o' war, the blue button (Porpita) and the by-the-wind sailor (Velella)
The source saysGlaucus species usually preys on pleustonic cnidarians like the by-the-wind sailor Velella velella (Linnaeus, 1758), the blue-button Porpita porpita (Linnaeus, 1758) and the Portuguese man-o'-war Physalia physalis (Linnaeus, 1758)Note: genus-level 'usually' kept; 'pleustonic' as 'drift at the surface'; 'stinging' rests on the nematocysts the next claims quote
The page saysIt uses its jaws and radular teeth to grab and tear their soft tissues and tentacles
The source saysGlaucus use their jaws and the radular teeth to grab and tear the soft tissues and tentacles of these cnidarians
The page saysIt swallows their stinging cells and concentrates them inside pouches called cnidosacs at the tip of each ceras
The source saysGlaucus species use the ingestion of both fired and undischarged nematocysts of their prey as a defensive strategy, concentrating them inside cnidosacs located at the tip of each cerata
The page saysContact with one that has fed on a man o' war can cause symptoms similar to a man o' war sting, including nausea, pain, vomiting, allergic skin reactions and possible blistering
The source saysHumans who have had contact with G. atlanticus that had feed on Physalia may present clinical issues similar to P. physalis envenomation ... including nausea, pain, vomiting, acute allergic contact dermatitis, erythema, urticarial papules, potential vesicle formationNote: 'allergic skin reactions' covers 'acute allergic contact dermatitis, erythema, urticarial papules'; 'possible blistering' is 'potential vesicle formation'
The page saysA man o' war's stinging cells can even cause death
The source saysThe nematocysts of those species may cause skin irritation ( Johnson and Allen 2012) or even death when Physalia toxin is involved
The page saysResearchers say a blue sea dragon should be considered as harmful to people as the animals it preys on, and that people should avoid touching one
The source saysGlaucus spp. should be considered as harmful to humans as their prey ... People should thus avoid direct contact with Glaucus spp.
The page saysYes. Researchers say it should be considered as harmful to people as the animals it eats. Contact with one that has fed on a Portuguese man o' war can cause symptoms similar to a man o' war sting, including nausea, pain, vomiting, allergic skin reactions and possible blistering. A man o' war's stinging cells can even cause death.
The source saysGlaucus spp. should be considered as harmful to humans as their prey ... The nematocysts of those species may cause skin irritation ( Johnson and Allen 2012) or even death when Physalia toxin is involved ... Humans who have had contact with G. atlanticus that had feed on Physalia may present clinical issues similar to P. physalis envenomation ... including nausea, pain, vomiting, acute allergic contact dermatitis, erythema, urticarial papules, potential vesicle formation

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.