Field guide · Last reviewed 22 September 2026
“Box jellyfish” describes an entire class of animals, not a single species. Some are palm-sized hunters in mangrove lagoons. Others trail tentacles long enough to make a swimmer stop in their tracks. Only a minority are known to cause life-threatening human envenomation, but identification is difficult enough that an unknown box-shaped jellyfish should always be treated with care.
Box jellyfish at a glance
Showing all 11 directory entries.
| Species | Best-known range | Useful clue | Human-risk context |
|---|---|---|---|
| Chironex blakangmati | Sentosa Island, Singapore Strait; described from Singapore material in 2026 | Elongated, sharp-tipped velarial canals; no canal extensions from the perradial lappet terminus | Venomous Chironex; the description did not establish a species-specific rate of severe human outcomes |
| Chironex fleckeri | Tropical northern Australia and nearby Indo-Pacific waters | Large bell; multiple tentacles arise from each corner | Can cause rapidly life-threatening envenomation |
| Chironex yamaguchii | Japan and parts of the western Pacific | Multi-tentacled Chironex form | Medically important; identification may require expert examination |
| Chironex indrasaksajiae | Originally described from Thailand; verified in the Johor and Singapore Straits in 2026 | Multi-tentacled Chironex; expert anatomy and voucher-linked DNA support separation | Venomous species; do not infer an individual sting outcome from a distant photograph |
| Carukia barnesi | Tropical Australia | Small, transparent, with one tentacle at each corner | Associated with Irukandji syndrome |
| Alatina alata | Tropical and subtropical waters, including Hawaii | Slender bell; some populations aggregate around lunar cycles | Can cause painful stings; medical effects vary |
| Morbakka fenneri | Eastern and northern Australia | Larger “Irukandji-type” box jellyfish | Associated with Irukandji syndrome |
| Tripedalia cystophora | Tropical mangrove habitats | Small species studied for sophisticated vision | Not regarded like the large lethal chirodropids |
| Copula sivickisi | Indo-Pacific | Small, active species with unusual courtship and mating | Not a leading cause of severe human envenomation |
| Carybdea marsupialis | Mediterranean and eastern Atlantic records | Single tentacle at each bell corner | Stings can be painful; severe effects are not the usual outcome |
| Chiropsalmus quadrumanus | Western Atlantic | Several tentacles per corner; identification is specialist work | Can cause medically significant stings |
Explore the species
Chironex blakangmati — Singapore’s 2026 species
Researchers described this fourth accepted species of Chironex from specimens collected at Sentosa Island along the Singapore Strait. It resembles C. yamaguchii in its volcano-shaped pedalial canal and tentacle count, but differs in fine velarial-canal anatomy and in 16S and COI DNA evidence. The paper did not provide a species-specific clinical case series, so this directory does not assign an unsupported lethality rate. See the 2026 comparison and evidence notes.
Chironex indrasaksajiae — a newly verified Singapore record
The 2026 study documented specimens from both the Johor and Singapore Straits around mainland Singapore, extending the published range beyond its original Thai records. This is a verified specimen-based range update, not evidence that the species suddenly arrived in 2026 or occurs on every Singapore beach.
Chironex fleckeri — Australian box jellyfish
The species most people picture when they hear “box jellyfish.” It is a large, powerful swimmer with clusters of tentacles hanging from muscular structures called pedalia. Its venom and extensive tentacle contact can produce a medical emergency within minutes. Read the full Chironex fleckeri guide.
Carukia barnesi — a tiny Irukandji jellyfish
Small size does not mean trivial risk. Carukia barnesi is one of several jellyfish associated with Irukandji syndrome, in which severe systemic symptoms can begin after a delay. “Irukandji” is therefore not a reliable species name.
Alatina alata — the lunar aggregator
This oceanic box jellyfish has become a useful research species because predictable near-shore aggregations occur in some locations around particular lunar phases. That fascinating pattern is local biology—not a calendar that predicts safety everywhere.
Tripedalia cystophora — mangrove navigator
A small mangrove species famous in vision research. Its eye-bearing sensory structures help it orient to habitat features even though it has no centralized brain like ours.
Morbakka fenneri — a larger Irukandji-type species
Sometimes called the Moreton Bay fire jelly, this species helped overturn the idea that every Irukandji-associated jellyfish must be tiny. It is a reminder that syndrome, body plan and species identity are different questions.
Other verified and emerging species
Chironex yamaguchii, Copula sivickisi, Carybdea marsupialis and Chiropsalmus quadrumanus represent different branches of Cubozoa. Taxonomy continues to move: DNA studies sometimes reveal deep differences among animals that look alike, while new species are still being formally described.
How scientists identify a box jellyfish
The squared bell is only the beginning. Researchers examine the number and arrangement of tentacles, pedalia, stomach structures, wart-like nematocyst patches and rhopalia. Our labeled box jellyfish anatomy guide explains those structures, while the guide to the eye-bearing rhopalia shows why one visible feature can contain several organs. Good identifications combine morphology with locality, preserved material and increasingly DNA. A beach photograph can narrow possibilities, but transparent bodies and damaged specimens make confident species-level identification surprisingly hard.
Family-level shorthand
- Chirodropids generally have branching pedalia with multiple tentacles at each bell corner. This group includes Chironex fleckeri.
- Carybdeids generally carry a single tentacle at each corner. The group includes small oceanic and near-shore species with very different medical importance.
These are useful starting points, not a do-it-yourself diagnostic key. Damaged animals, juveniles and newly recognized lineages can defeat a simple visual rule.
Why the exact name matters
Species names connect observations to evidence: a verified distribution record, a venom study, a spawning event or a clinical report. Treating every cubozoan as equally lethal exaggerates some risks and hides others. The more responsible approach is to separate what has been documented for a species from what is inferred from its relatives.
What to record without touching the animal
- Photograph it from a safe distance, including the bell and tentacle arrangement if visible.
- Record the exact place, date, time and whether it was in the water or stranded.
- Note recent wind, tide and local warnings without assuming they caused the sighting.
- Send the record to the relevant museum, marine authority or verified citizen-science program.
Never collect a specimen unless a qualified authority has asked you to and supplied a safe protocol. Detached tentacles and dead jellyfish may retain unfired stinging cells.
A 2026 identification update: the Chironex family got clearer
A species directory should be a record of changing evidence, not a frozen list. On 15 May 2026, Iesa and colleagues described Chironex blakangmati from Sentosa Island and documented Chironex indrasaksajiae in both the Johor and Singapore Straits. The latter is a range extension in the scientific record—not proof of a recent biological arrival. The peer-reviewed description is published in the Raffles Bulletin of Zoology (doi: 10.26107/RBZ-2026-0026).
The new species was not separated by location or bell shape alone. The authors combined voucher specimens, fine anatomy and molecular phylogenies. C. blakangmati shares a volcano-shaped pedalial canal and a similar tentacle count with C. yamaguchii, yet has elongated, sharp-tipped velarial canals and lacks canal extensions from the terminal end of the perradial lappet. Analyses of the 16S rRNA and COI markers also placed it apart from the other sampled Chironex; the authors explicitly noted that COI sampling was more limited.
That is a useful warning for non-specialists: bell shape, transparency and location can narrow an identification, but they rarely prove a species. A responsible record connects a photograph or specimen to a place, date, measurement method, diagnostic anatomy, voucher collection and, when available, molecular evidence.
| Evidence | What it can support | What it cannot establish alone |
|---|---|---|
| Geolocated photograph | Presence of a box-shaped medusa at a recorded place and time | A confident species name when key structures are hidden |
| Bell and tentacle measurements | Comparison with described size ranges | Identity when juveniles and adults overlap in size |
| Pedalia, tentacle branching and bell canals | Important order-, genus- and species-level clues | A complete identification if the specimen is damaged |
| Voucher specimen | Repeatable examination by later researchers | Correct identity without suitable comparisons |
| DNA sequence tied to a voucher | Comparison with reference sequences and cryptic lineages | A reliable name if the reference library is misidentified |
Chironex comparison plate
| Species | 2026 evidence snapshot | Identification caution |
|---|---|---|
| C. blakangmati | Sentosa Island specimens; distinctive velarial-canal pattern plus 16S and COI evidence | Its overall form can resemble C. yamaguchii; expert anatomy or voucher-linked DNA may be needed |
| C. yamaguchii | The closest look-alike discussed in the revision; adult and juvenile velarial canals were compared | Canal form changes during growth, so age and specimen condition matter |
| C. indrasaksajiae | Voucher-backed records from the Johor and Singapore Straits extended its documented range | A new record is not the same as a newly arrived population |
| C. fleckeri | Included as a comparative congener in the anatomical review | Familiar common names and broad regional labels cannot substitute for specimen-level diagnosis |
How accepted names enter this directory
We use the original description or subsequent peer-reviewed revision for diagnostic claims, then check the current genus list in the World Register of Marine Species (WoRMS) for accepted-name status. As checked on 22 September 2026, WoRMS lists four species in Chironex: C. blakangmati, C. fleckeri, C. indrasaksajiae and C. yamaguchii. Database inclusion supports current nomenclature; it does not independently validate every distribution, venom or identification claim.
- Start with the name-bearing evidence. Prefer the original description, designated types and voucher-linked data over copied species lists.
- Check the accepted name and access date. If WoRMS treats an older name as a synonym, the accepted name leads and the synonym remains searchable.
- Keep geography evidence-specific. A verified locality is not automatically a complete range map; compare records in the species-by-species distribution guide.
- Separate sting evidence from species reputation. A medically important genus does not make every unverified sighting equally dangerous.
- State uncertainty. Juveniles, damaged specimens and incomplete DNA reference libraries can limit confidence.
How to read this directory
- Start with geography, but do not stop there. A known range is supporting context, not proof.
- Check the accepted name and access date. Taxonomy changes as old specimens are re-examined and new evidence appears.
- Separate sting evidence from species reputation. A medically important genus does not make every unverified sighting equally dangerous.
- Follow the evidence trail. The strongest profiles distinguish original descriptions, later revisions, verified records and open questions.
Quick challenge: would you name a species from one beach photograph?
Usually no. A safe public report can say “possible box jellyfish” and preserve the original image, date and location. A species-level identification may require anatomical examination or a voucher-linked DNA sequence.
Directory change log
- 22 September 2026: added Chironex blakangmati; added the voucher-backed Singapore records for C. indrasaksajiae; updated the Chironex count to four; added the accepted-name method, evidence table, comparison plate and directory filter.
- 22 August 2026: launched the evidence-led species comparison and identification cautions.
Selected sources
- Iesa, I., Lewis Ames, C., Yap, N. W. L. & Huang, D. (2026). Chironex box jellyfishes in Singapore. Raffles Bulletin of Zoology 74: 383–402. doi: 10.26107/RBZ-2026-0026.
- World Register of Marine Species: accepted Chironex species (accessed 22 September 2026)
- Smithsonian Ocean: jellyfish and comb jellies
- Australian Museum: Australian box jellyfish
- NOAA repository: genetic study of Chironex yamaguchii
Editorial note: taxonomy and accepted distributions change as specimens are re-examined. We date substantive revisions and welcome documented corrections.