---
title: "What the sources say about the Blue Sea Dragon | AnimalTracks.wiki"
description: "39 claims from the Blue Sea Dragon profile, each beside the words of the source that backs it."
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# What the sources say about the Blue Sea Dragon (*Glaucus atlanticus*)

> 39 claims from the Blue Sea Dragon profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Blue Sea Dragon](https://animaltracks.wiki/animals/blue-sea-dragon/)

## Blue Glaucus. Oceana.

https://oceana.org/marine-life/blue-glaucus/

| The page says | The source says |
| :--- | :--- |
| Air-bubble buoyancy | staying afloat by storing air bubbles in their stomach |
| Not Evaluated | little is known about its conservation status (note: 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).) |
| is a nudibranch, a shell-less sea slug | this tiny sea slug ... the blue glaucus is a species of nudibranch, a group of soft-bodied, shell-less marine gastropods |
| a slug that floats upside down at the surface | they spend most of their lives floating upside-down at the surface |

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

https://www.boem.gov/newsroom/ocean-science-news/blue-dragon-sea-slug

| The page says | The source says |
| :--- | :--- |
| Surface of the open ocean | Ecosystem: Surface of the open ocean |
| steals a Portuguese man o' war's stinging cells and stores them in its own cerata | venomous creatures such as Portuguese Man O’ War ... Glaucus atlanticus appropriates the victim’s stinging cells and stores them in its cerata |
| about 3 centimeters long, barely over an inch | approximately 3 cm (1.2 in) in size (note: Oceana gives 'about 2.5 centimeters (1 inch)'; the dated 2024 BOEM page is used) |
| It spends its life drifting at the surface of the open ocean | Ecosystem: Surface of the open ocean ... is an ocean drifter, spending its life carried by ocean currents and the wind |
| tendril-tipped appendages called cerata that spread like wings | it has three pairs of tendril-tipped appendages that spread like wings, getting shorter as they go down its body |
| A borrowed sting, concentrated | appropriates the victim’s stinging cells and stores them in its cerata in a more highly concentrated dosage |
| The 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 | appropriates 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 sting (note: replaces the 1998 Sea Slug Forum 'much more deadly' comparison, which the 2019 paper ('as harmful to humans as their prey') contradicts) |
| Blue sea dragons sometimes wash ashore, and an encounter with even a dead one can result in getting stung | The 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 |
| It lives in tropical and temperate waters of the Atlantic, Pacific and Indian oceans | Tropical and temperate waters of the Atlantic, Pacific, and Indian Oceans (note: BOEM's Distribution line (release date 03/19/2024).) |

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

http://www.seaslugforum.net/find/glauatla

| The page says | The source says |
| :--- | :--- |
| blue-and-silver countershading | They 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 |
| tropical and temperate waters circling the globe | Circumglobal in temperate and tropical waters. (note: 'circling the globe' for 'circumglobal') |
| Along with the rest of the "blue fleet" of surface-dwelling animals it drifts among, it is carried by the currents and the winds | live 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. |
| Because it floats upside down, its foot faces the sky, and its colors are a textbook example of countershading | They 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 foot is blue, which helps camouflage it from seabirds hunting above | Their foot and undersides of the cerata, ... is blue or blue and white which helps to camouflage them from predation (sea birds) from above |
| Its true back faces down and is silvery grey, camouflaging it from fish looking up from below | Their true dorsal surface, which faces down in the water, is silvery grey to effectively camouflage them from fish looking up from below. |
| It also appears to select the man o' war's most venomous stinging cells to store | it appears that they are able to select the most venomous of Physalia's stinging nematocysts for their own use |
| It 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. | All 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. |
| carried by the currents and the winds | All these animals float on the surface of the ocean being carried by the currents and the winds. |

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

https://doi.org/10.1002/ecy.70062

| The page says | The source says |
| :--- | :--- |
| Kleptocnidae | Glaucus species engage in kleptocnidae, recycling nematocysts from cnidarians |
| kept afloat partly by air bubbles in its stomach | all species of Glaucus are pleuston ... species that live on the ocean's surface, using cerata and air bubbles in their stomach cavities for buoyancy (note: 'partly' because the cerata also give buoyancy) |
| Down each side of its body | all species of the genus Glaucus ... on each side of their bodies |
| Scientists long thought cerata were mainly for defense | It has long been postulated that kleptocnidae and cerata in Cladobranchia are mainly defensive organs |
| A 2025 study that reared the slugs in aquaria filmed something else | Issue date 2025 Mar. ... we report that Glaucus atlanticus successfully reared in aquaria employ their cerata for prey capture (note: '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 )'.) |
| Some 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 | When 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 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 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 |
| It 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. | Nematocysts 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 |

## 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.

https://doi.org/10.1590/0001-3765201920180154

| The page says | The source says |
| :--- | :--- |
| a sting borrowed from the Portuguese man o' war | Glaucus 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 |
| Portuguese man o' war, blue buttons (Porpita), and by-the-wind sailors (Velella) | 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) |
| The 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) | Glaucus 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) |
| It uses its jaws and radular teeth to grab and tear their soft tissues and tentacles | Glaucus use their jaws and the radular teeth to grab and tear the soft tissues and tentacles of these cnidarians |
| It swallows their stinging cells and concentrates them inside pouches called cnidosacs at the tip of each ceras | Glaucus 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 |
| Contact 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 | 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 (note: 'allergic skin reactions' covers 'acute allergic contact dermatitis, erythema, urticarial papules'; 'possible blistering' is 'potential vesicle formation') |
| A man o' war's stinging cells can even cause death | The nematocysts of those species may cause skin irritation ( Johnson and Allen 2012) or even death when Physalia toxin is involved |
| Researchers 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 | Glaucus spp. should be considered as harmful to humans as their prey ... People should thus avoid direct contact with Glaucus spp. |
| Yes. 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. | Glaucus 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 |