Venomous beauty

Sheree Marris | VOLUME 29, ISSUE 2
Stingrays are generally shy, but can be dangerous if disturbed.
Beautiful but potentially lethal, some aquatic creatures are best admired from afar.

Our oceans are home to some of the most spectacular and venomous animals on the planet, with an estimated 1200 different species of venomous fish making up a large part of this infamous population.

When mentioned, the word 'venom' instils a sense of fear and with good reason: venom can transform small and seemingly harmless creatures into some of the ocean's most fearsome killers, with even blind and toothless animals that can barely swim being turned into floating death traps.

The diversity with which sea creatures use venom is impressive. Think venomous harpoons shooting out of mouths, bird-like beaks with paralysing saliva, and arms laced with billions of biological booby traps.

How and why an animal deploys its venom depends on the species. Some use it to subdue prey while, for others, it's a deterrent used only in self-defence. What all venoms do, however, is disrupt normal physiological or biochemical processes that can leave victims writhing in pain or, at its worst, dead.

Venomous defences

Throughout the plant and animal kingdoms, venom is used as a means of self-defence

Lionfish

Everything about this fish screams 'I'm dangerous don't mess with me'. It has an impressive 'mane' fashioned from venomous spines and extravagant pectoral fins decorated with bold stripes .

Try to wrestle or eat this lion and you'll be served a meal of long, venomous spines. If you're a shrimp or fish trying to avoid a lionfish, its camouflage and lightning-fast reflexes will devour you before you know what's hit you.

It's one of the most resilient fish on the reef, eating up to 60 per cent of its body weight every day or going for weeks without any food at all. So much so, it's now classified as a pest in some areas and encounters with humans are becoming more common.

Stingrays

Stingrays have had their share of negative publicity of late, but undeservedly so. These winged-wonders are far from aggressive, but the ocean can be a dangerous place to live and they need to protect themselves. Their weapon of choice: a venomous barbed spine that sits on the tail.

When unleashed, the barb detaches from the tail and embeds itself in the victim. Venom flows along the barb causing intense pain by forcing muscles to contract. It's the serrations on the barbs that cause the most damage: the barb enters smoothly but on exit, it rips soft tissue to shreds. Unfortunately, some stingrays like to rest hidden underneath a cloak of sand, making them difficult to see so that they're accidently stood on.

Stonefish

Stonefish have the bragging rights as being one of the most deadly fish in the sea, with venomous dorsal fin spines that can be lethal. The upside is that they don't use these spines for hunting. On the downside, they're masters of camouflage and often impossible to see.

As the name suggests, stonefish look like a stone, allowing them to blend seamlessly into the surroundings. They're so confident with their camouflage they rarely swim off, even encouraging plants and animals to settle on their skin for an added au naturel look. When they feel threatened or are accidently stepped on, however, they may erect their poisonous dorsal fins in pre-emptive defence.

Crown-of-thorns

This starfish has a voracious appetite and an infamous reputation for destroying coral reefs. A crown-of-thorns starfish's pretty looks serve as a warning: look but don't touch. This is one sea star you don't want to pick up - of the nearly 2000 species of sea stars known, this is the only one thought to be venomous.

The topside of their body is covered in sharp spines packed with venom, which deters most creatures from dining on them, although some creatures, like triton shells, will happily dance with death and live to tell the tale. For humans, a brush with the crown-of-thorns is, thankfully, only met with tingles, pain, heat and a whole lot of embarrassment (as the author can attest to).

Flower urchins

All sea urchins have long sharp spines, which can easily penetrate skin when picked up or accidentally stepped on. Needless to say, this can be painful, but not life-threatening.

Few people know that some of these beauties are venomous. Enter the flower urchin: instead of spines, its round body is covered in what looks like pretty pink flowers. But don't be fooled - smelling these flowers can be dangerous. Fashioned at their tips are jaw-like appendages that not only help keep the sea urchin clean, they protect the urchins by injecting toxic venom when touched. Flower urchins are often found partially buried in sand, so watch your step.

Venomous attacks - using venom to subdue prey

Blue-ringed octopus

Imagine being able to induce fear and rule the rock pools with saliva ... what might sound a bit absurd is the weapon of choice for the blue-ringed octopus. Small and weighing a mere 10g, it's one of the most lethal animals on earth.

Sneaking up from behind, this little jet-powered jewel wraps its eight arms around its prey, engulfing it like a cape. A bird-like beak then bites through the flesh or shell of its victim releasing one of the most lethal venoms known - TTX (Tetrodotoxin), a deadly neurotoxin made by the octopus's in-house bacteria. It's the same potent chemical found in poison dart frogs that quickly paralyses its prey. With its beak, the blue-ring octopus then rips and tears at its prey, while special digestive enzymes liquefy the body parts.

Sea snakes

It's said the most dangerous snakes are the ones you don't see, but ask any diver and they'll say an encounter with these serpents of the sea is a highlight of a dive.

Docile and inquisitive, sea snakes don't pose any threat unless you're a small fish or crustacean. If you're unfortunate enough to fall into this category, the end will come via a pair of fangs containing a cocktail of two venoms. The first venom stops the body from functioning and the second turns flesh and muscle into mush. Coupled with the ability to dislocate their jaws, these sea serpents can even attack large prey.

Most bites to humans occur when fisherman pull up nets with trapped sea snakes, which would understandably be cranky. The upside is that less than a quarter of bites will contain venom.

Portuguese man-o'-war

With a name derived from an old nautical term for a sailing warship, it's not surprising that the Portuguese man-o'-war is equipped with some serious firepower.

Often confused with jellyfish, this creature is not one animal, but a crew of four separate colonies of organisms working together. Each has a specific role to play in the running of the ship: a float keeps the ship sailing, the reproductive organisms do their thing, the firepower comes from venom-filled tentacles that dangle elegantly from the main float, discharging on contact. The spoils are then passed onto the 'crew' who digest the catch.

Washed up dead and even detached tentacles from these delicate beauties can still sting and leave red painful welts on the skin.

Box jellyfish

Although they're slow, have no teeth and are mostly made up of water, it's wise not to underestimate box jellyfish. They're the most venomous predators in the ocean and range from the big box jellyfish, reaching 30cm across the bell with tentacles 3m long, to the Irukandji jellyfish measuring a tiny 2cm.

What they all have in common are the millions of biological booby traps their bodies are covered in. A mere touch of their tentacles launches batteries of venomous harpoons that would turn any fish or shrimp into jelly. Their firepower is impressive, with the whole stinging process taking just 0.9 micro-seconds - one the fastest biological processes known.

Cone shells

Cone shells are mobile artillery factories that crawl around on a single sticky foot. They manufacture and stockpile an arsenal of barbed teeth ready to unleash on any prey they can sniff out with their trunk-like proboscis.

When in firing range, the cone shell shoots out a venom-filled harpoon at its target. Trapped on the harpoon, the helpless victim is dragged back and devoured by the snail's expandable mouth.

A cone shell's venom varies with its preferred prey. Humans are more susceptible to the venom of cone shells that eat other vertebrates such as fish. It's worth noting that the proboscis is flexible enough to reach any part of the cone shell's body, so no part of the animal is safe to pick up.

Points of difference

Though the two terms are often used interchangeably, venom is not the same thing as poison. The difference is in the delivery: poisons are ingested or absorbed through the skin; venom is injected directly into another animal by stinging, harpooning, or biting.

Venomous benefits

Venom is obviously something to be avoided at all costs, but scientists can't seem to get enough of it. They're discovering the many benefits of venoms and using some to develop new drugs. A cone shell species, for example, has been found to contain compounds within its venom that produce a pain killer 1000 times stronger than valium, while others are proving efficient as a treatment for ailments such as Alzheimer's and Parkinson's disease.

Unlocking the secrets of venom and learning of their benefits may take years, but in the meantime we will continue to marvel at the animals that are reaping their own benefits from such powerful stuff.

Safety tips

While it's great to observe these amazing creatures in the wild, they should be approached with caution and admired from a distance. Some tips to keep you safe while in the water:

* As a general rule-of-thumb, don't touch anything unless you know what it is and whether it's safe to do so
* Do the 'stingray shuffle' when wading in the water to scare off any venomous creatures buried in the sand - this will kick and scare off creatures hiding in or on the sand, rather than stepping on them
* Wear protective clothing such as wetsuits and rash vests to protect from stings and spines
* Give the animals plenty of space and don't harass or chase them
* Don't put your hands where you can't see them
* If you do have an unlucky encounter, seek medical attention immediately.


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