Animal: Carukia barnesi, Irukandji

Taxonomy

Common names

Distribution

Western, northern and eastern Australia. Most probably a large distribution area in the Indo-Pacific. Cases of envenoming involving an "Irukandji-like" syndrome (see below) known in New Guinea and Hawaii.

Biology

Carukia barnesi is a box jellyfish that lives in the open sea and can be found at different water depths. It is only through strong currents that they are sometimes carried in large swarms into coastal waters. They can be encountered in the outer reefs of the Great Barrier Reef, and less often directly off the beach. As is characteristic for box jellyfish, the bell is more or less square in shape. There is a tentacle attached to each of the 4 lower corners. Alone due to its size it is unlikely to be mistaken for Chironex fleckeri or Chiropsalmus quadrigatus. Its bell is roughly the size of the distal joint of a thumb (diameter approx. 2.5 cm). Unlike in the larger box jellyfish, the nematocysts, which are what makes the animals dangerous for humans, are not located on the tentacles but rather on the bell.

Interestingly, this species was first discovered in the search for the cause of the well-known envenoming syndrome known as the "Irukandji syndrome". A weaker form of this syndrome can also be caused by other carybdeid jellyfish, which have not yet been conclusively classified in taxonomic terms, as well as by Stomolphus nomurai (Chinese coast) and Gonionemus sp. (northern Japan and Vladivostok).

Carukia barnesi

Risk

Until a few years ago, no fatalities had been reported. Then in 2002, two cases of fatal envenoming associated with Irukandji syndrome were published (Fenner and Hadok 2002). Untreated envenoming may thus indeed be fatal. The envenoming syndrome is associated with a generalised release of catecholamines.

Contact with this jellyfish barely leaves marks on the skin (see figure: 'Ecological, morphological and medical characteristics of dangerous jellyfish in the Indo-Australian region').). If the initial pain is ignored and the victim enters the water again, the symptoms, which appear with some delay, can lead to drowning.

In Queensland, Australia, there have been epidemic-like cases of envenoming, in which 40–50 bathers have been stung on the same day due to a mass occurrence of Carukia barnesi. The special stinger nets that are placed around beaches in Australia to protect against Chironex or Chiropsalmus do not keep out the Irukandjis because of the large size of the mesh. Thus nets with a smaller mesh were introduced, but there are still sometimes occurrences of Carukia stings inside the netted areas.

There are regularly accidents involving divers, as the tiny Irukandjis can cause stings on the smallest unprotected areas of skin, such as on the neck or on the face. In this case the syndrome may be falsely interpreted as decompression sickness!

Other species of carybdeid jellyfish that may cause Irukandji syndrome (Gershwin et al 2013: “Table 1.2 Summary of ecology and syndrome characteristics of species known or believed to cause Irukandji syndrome”; Tibballs et al 2012; Debate: Little et al 2006, Gershwin 2006, Fenner 2006):

Alatina mordens, Carukia shinju, Carybdea alata, Carybdea rastonii, Carybdea xaymacana, Malo maxima, Malo kingi, Alatina mordens, Gerongia rifkinae, and Morbakka fenneri

Literature (biological)

Bentlage and Lewis 2012, Cleland and Southcott 1965, Cunha and Dinis-Oliveira 2022, Fenner 1988, Fenner and Hadock 2002, Gershwin 2005, Kinsey 1988, Williamson and Exton 1985, Warrell and Fenner 1993, Williamson et al. 1996