Venomous marine animals

Box Jellyfish or Sea Wasp (Chironex fleckeri)

Box Jellyfish (Chironex spp)

About

The Box jellyfish (Chironex fleckeri) is the most dangerous jellyfish, and indeed one of the most dangerous venomous creatures, in the world. It is a large jellyfish, weighing up to 6 kg and measuring about 20-30 cm across the bell. The tentacles may stretch up to 2 metres. It is transparent in the water, and therefore difficult to see. It has 4 bundles of tentacles, which may number  up to 60 in total.  Each tentacle contains many millions of nematocysts or stinging cells (see photo below) which discharge venom through the skin on contact. Contact with a large amount of tentacular material over a wide surface area can result in massive envenomation. Most stings occur in the summer months in shallow water near the beach, and are particularly common in children

Distribution

Found in the coastal waters of northern Australia, from Gladstone in Queensland to Broome in Western Australia, but not on the Great Barrier Reef, during the summer months

Venom

Nematocysts, or stinging cells, are used by jellyfish to deliver toxins into their prey.  The stinging apparatus consists of a "harpoon" on a thread coiled inside the stinging cell, and attached to a reservoir containing venom.  On contact with the victim, the stinging cell discharges its harpoon into the skin and injects venom. Each tentacle may be covered with millions of stinging cells, resulting in a large amount of venom being injected over a wide area.

Precautions that should be taken to avoid potentially fatal Box jellyfish envenomation include:

• Avoid swimming in areas where Box jellyfish are found during the jellyfish season (variable, but approximately September to March) and heed warning signs on beaches. N.B. avoid swimming alone or at remote beaches.
• Wear specially designed "stinger suits"  (pictured) while in known Box jellyfish waters
• Swim at beaches patrolled by life savers, preferably equipped with vinegar, antivenom and basic resuscitation facilities
• Exercise caution on entering the water (do not dive or run into the water)
• Strictly supervise children, who are more prone to stings, and whose lower body weight may render them more susceptible to the effects of the venom
• Swim at beaches that have been netted to exclude box jellyfish
  (N.B. this will not prevent Irukandji stings (see below), as these animals are much smaller than box jellyfish, and can fit through the gaps in the mesh of jellyfish nets)

Irukandji (Carukia barnesi)

About

Carukia barnesi (the Irukandji) is a small  jellyfish (~2cm diameter bell) responsible for an unusual and dramatic syndrome observed following stings in northern Australia, especially north Queensland. Unlike Chironex fleckeri, Irukandji are found mostly in the deeper waters of the reef, although they may be swept inshore by prevailing currents. Divers and snorkellers are particularly at risk.

Distribution

Stings have been recorded from Childers to Broome, and a similar syndrome has been described elsewhere in the Pacific

Venom

The sting itself is only moderately painful, with little associated tissue damage, but approximately 30 minutes later, the patient develops a complex of systemic symptoms including severe back and abdominal pain, limb or joint pain, nausea and vomiting, profuse sweating and agitation. No definitive treatment is currently available for the Irukandji syndrome.

Portuguese Man-o-war or Bluebottle (Physalia sp.)

Bluebottle. Photo Jim Woulfe. Creative Commons 2.0.

About

The Portuguese man-o-war or bluebottle, (Physalia sp.), is well known throughout Australian waters (and both the pacific and Atlantic oceans) for causing painful stings. No fatalities have been confirmed in Australia. The float measures 2-15 cm. The main or fishing tentacle may be up to 10m long and is responsible for most of the stings. The larger Atlantic specimens probably represent more of a threat to human life. In human envenomation, pain is the most prominent feature, along with localized skin lesions with a "string of beads" appearance; discrete weals surrounded by erythema. Systemic symptoms are uncommon but may include headache, nausea and vomiting, abdominal pain and occasionally collapse. First aid consists of removal of the tentacles, preferably with forceps. Vinegar is not recommended. Analgesia may be required, although most stings respond to ice packs and/or topical anaesthetic agents.

Distribution

Throughout Australian waters (and both the Pacific and Atlantic oceans)

Venom

The venom contains lethal and haemolytic components and has been shown to produce nerve conduction disturbances, flaccid paralysis and smooth muscle contraction in experimental animals.

The sea blubber or hairy stinger (Cyanea sp)

Lion's Mane Jellyfish (Cyanea capillata). Photo Dr Isobel Bennett © Australian Museum

About

These jellyfish have a flattened or plate-like bell, and multiple delicate hairy tentacles.  The bell may be 30cm across in Australian jellyfish, and significantly larger in the cold-water Atlantic jellyfish.

Distribution

Widely distributed, and found in coastal waters throughout Australia.

Venom

Stinging results in severe pain that may last for up to an hour.  Nausea and abdominal pain sometimes occur, as do sweating, muscle cramps and breathing difficulties.  No deaths have been attributed to this creature.