--- title: "Irukandji Jellyfish (Carukia barnesi) | AnimalTracks.wiki" description: "A box jellyfish that fishes for larval fish by twitching its tentacles like lures." image: "https://animaltracks.wiki/images/animals/irukandji-jellyfish-1.webp" published: "2026-10-11" updated: "2026-10-11" --- # Irukandji Jellyfish (*Carukia barnesi*) > **Status**: Checked against 8 sources, listed under Sources below. > **Tagline**: A box jellyfish that fishes for larval fish by twitching its tentacles like lures. > **Soundtrack Vibe**: IDM & Glitch Ambient Synthesis // Jon Hopkins, "Emerald Rush" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/5S3F5GL8LASIjPg2PMiU1Q) > **Vibe Match**: In light, the jellyfish twitches its tentacles about 6.3 times a minute, showing off lure-like clusters of stinging cells that attract larval fish. Jon Hopkins' Emerald Rush flickers a bright melody over a steady, pulsing beat. ## Biological Superpowers & Stats - **Taxonomy**: *Carukia barnesi* - **Danger Level**: Deadly - **Conservation Status**: Not Evaluated ([IUCN Red List](https://www.iucnredlist.org/)) - **Superpower**: Twitches its tentacles like fishing lures to draw in larval fish - **Habitat**: Open water around coral reefs and islands off north-eastern Australia - **Diet**: Crustaceans when young; larval fish as an adult - **Tags**: cnidarian, venomous, ocean ## Natural History & Behavior ## A fishing lure with a sting *Carukia barnesi* is a small box jellyfish. A 2015 study gives its bell, the jelly body, as approximately 20 millimetres wide. A 2016 study says the bell height reaches up to 35 millimetres and the tentacles up to 1.2 metres. Four tentacles hang from the four corners of the bell. Each carries clusters of stinging cells in an alternating pattern of large and small. Adults use those clusters as bait. In a tank, in light, the jellyfish extends its tentacles and twitches them. The average twitch rate in the light was 6.3 twitches per minute, and no twitching was recorded in the dark. Larger animals twitched their tentacles more often than small ones. The clusters attract larval fish, which are then stung and eaten. It has four sets of six eyes, which is typical among cubozoans, the box jellyfish group. One pair in each set are complex eyes with a cornea, a lens and a retina, though how sharply they see, and what they are used for, is unknown. ## The syndrome that arrives late Irukandji syndrome is linked to this jellyfish, and other small Australian box jellyfish may be linked to it too. The sting behind it is characteristically relatively minor. The syndrome develops after about 30 minutes and consists of severe muscle pains, especially of the lower back, muscle cramps, vomiting, sweating, agitation and high blood pressure. In severe cases there can be acute heart failure. Envenoming by *C. barnesi* may produce life-threatening Irukandji syndrome. ## Where it lives and how it grows The medusa, the free-swimming jellyfish stage, is present in north Queensland waters between November and May. It is present along the north-eastern coast of Australia from Lizard Island to Fraser Island. The medusa is considered oceanic and planktonic, and has been found around coral reefs or islands. Young jellyfish feed predominantly on crustaceans. Adults feed predominantly on larval fish. > **Waiting game** In a lab study, most fertilised eggs developed into larvae called planulae that paused for between six days and six months before hatching. In the same study, the hatched larvae settled and turned into polyps. Mature polyps budded off swimming polyps from their sides. A polyp that made a medusa was left behind, still able to reproduce asexually. A newly detached lab medusa had a bell height of 0.33 to 0.80 millimetres. ## Frequently Asked Questions ### Can an Irukandji jellyfish kill a person? A 2010 case report describes the death of a healthy 44-year-old man stung while swimming in north-eastern Australia. He developed Irukandji syndrome, then a bleed inside the brain. The authors call it the first death from the syndrome where Carukia barnesi was shown to be the cause. *(Source: [Pereira et al. 2010]())* ### Does its venom change as it grows? In one study, tentacle venom from young and mature animals showed different protein bands. The authors link that to the shift from invertebrate prey in young jellyfish to vertebrate prey in mature ones. *(Source: [Underwood & Seymour 2007]())* ### How many people at one hospital had Irukandji syndrome? Cairns Base Hospital records for the year from July 2001 to June 2002 showed 128 patients with marine stings, and 116 of them had Irukandji syndrome. Skin scrapings from 50 patients were checked, and 39 held stinging cells consistent with Carukia barnesi. *(Source: [Huynh et al. 2003]())* ## Sources 1. [Courtney, Browning & Seymour (2016). Early Life History of the 'Irukandji' Jellyfish Carukia barnesi. PLOS ONE.]() 2. [Courtney et al. (2015). Prey Capture Ecology of the Cubozoan Carukia barnesi. PLOS ONE.]() 3. [Pereira et al. (2010). Intracerebral hemorrhage and death after envenoming by the jellyfish Carukia barnesi. Clinical Toxicology.]() 4. [Huynh et al. (2003). Severity of Irukandji syndrome and nematocyst identification from skin scrapings. Medical Journal of Australia.]() 5. [Underwood & Seymour (2007). Venom ontogeny, diet and morphology in Carukia barnesi, a species of Australian box jellyfish that causes Irukandji syndrome. Toxicon.]() 6. [Tibballs et al. (2012). Australian carybdeid jellyfish causing 'Irukandji syndrome'. Toxicon.]() 7. [Ramasamy et al. (2005). The in vivo cardiovascular effects of the Irukandji jellyfish (Carukia barnesi) nematocyst venom and a tentacle extract in rats. Toxicology Letters.]() 8. [Carukia barnesi. Animal Diversity Web, University of Michigan.]() *Published October 11, 2026. 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