Dangerous species

This symbol indicates marine creatures which are among the most venomous creatures on earth.

Marine creatures within the reef ecosystem have evolved different types of predatory and defensive mechanisms in order to survive such as stings, spines and venomous bites. Many of these are among the world's most venomous creatures. Animal Planet's 'Most Extreme: Venom' program included in its top 10 list the box jellyfish, stonefish, blue-ringed octopus, cone shells and sea snakes. Many of these except perhaps for the box jellyfish can be found in Redang.

Fortunately for us, these creatures are not out to attack humans. We are not their natural targets or food source and they are not naturally aggressive toward us. It is only when our presence and behaviour threatens and provokes them that we may become victims of their defenses. Most human injuries are typically a result of accidental contact with these creatures. Under normal circumstances, the natural reef is not dangerous. Most unpleasant encounters involving reef life are caused by people accidentally touching them, stepping on them or simply due to ignorant and stupid actions. We can minimize accidental contact with them by observing the general precautions shown in the box above.

With many reef predators and prey occupying the same reef habitat, many reef creatures would rather hide when threatened and employ deception, mimicry and camouflage to disguise themselves as a first line of defense. Some even show off bold, bright colours to announce that they are poisonous. Others will distract predators with inks, lights or ejected parts. When attempts to evade the attacker is futile, they will resort to different means to protect themselves, including using predatory mechanisms as a last line of defense.

Slow-moving creatures like urchins, sea stars and cone shells use chemicals or poisons in combination with darts, spines and needles to protect themselves.

Stonefish and scorpionfish carry lethal venom on dorsal spines, rays carry venom in their stings, while boxfish, pufferfish, soapfish and toadfish secrete skin poisons.

Jellyfish, corals, anemones and hydroids use stinging cells called nematocysts to fire a mass of minute harpoons containing venom to stun and kill their prey.

Some species of octopus have venom in their saliva. For example, the bite from the tiny blue ringed octopus can be lethal to humans.

Some innocent-looking reef fishes are equipped with self-defense mechanisms. Squirrelfish and angelfishes have spines on their gill-covers which are venomous in some species of squirrelfish. Surgeonfish have a retractable blade or scalpel at the base of the tail which it uses to slash would-be attackers.

Some sea cucumbers eject white cuiverian tubules when irritated. These contain toxins that can cause blindness when it comes into contact with the eye - so make sure you wash your hands after handling them. Others are able to cast off parts of their gut as sacrificial bait or emit sticky filaments to entangle would-be predators, including humans. These body parts are regenerated.

Barracudas, sharks, eels and triggerfishes have powerful jaws for biting while the mantis shrimp uses its deadly claws to spear or smash their victims. Electric rays and electric eels can deliver high-voltage electric shocks to stun its prey.

Blue-ringed octopus

This golf ball-sized octopus is small, about 7 cm long, shy and hides in coral crevices or under rocks. It may look cute, harmless and attractive but is amongst the most dangerous creatures on the reef. Its venomous bite has claimed a number of human lives as its saliva contains TTX (tetrodotoxin) produced by bacteria, one of the most potent neurotoxins known for which there is currently no known antidote. TTX is also found in certain organs in the puffer fish which have killed some connoisseurs of 'fugu' as it is known in Japan.

The blue rings on its body are only clearly visible and pulsate when the octopus is agitated and about to bite. The bite is slight, reported to be accompanied by little or no pain, but will lead to muscular paralysis and respiratory failure.

For more information, read Dr. Roy Caldwell's article on blue-ringed octopuses.

Sea snakes

Sea snakes have scales and flattened, paddle-like tails with heads that resemble land snakes whereas eels, being fishes, have a fish-like face and mouth as well as one long continous dorsal fin.

All sea snakes are highly venomous and should not be handled even though they are shy, gentle and do not normally pose a threat unless provoked. When they do bite, in about 65% of cases, they don't use their venom. Antidotes are available for treatment.

Sea snakes may approach divers out of curiosity. The best defense is to stay calm and the snake will continue on its way. As with other reptiles, they breathe air and have to periodically return to the surface. They are usually found in depths between 5 to 10 metres.

Scorpionfish and stonefish

The family of fishes known as Scorpaenidae all have venomous spines on their dorsal fins as a defense against bottom feeding rays and sharks. Some species also carry these spines on their pectoral and anal fins.

All of them, except for the brightly coloured lionfishes, are well camouflaged, blending with their surroundings and remaining stationary. Hunting mainly at night, they sit and wait until an unwary prey comes near, then they pounce on it at lightning speed, swallowing it. Lionfishes tend to move in search of prey.

The stationary scorpionfishes are usually given away only by their large pectoral fins and slightly\ curled up resting stance on the sea bed, corals or rocks. They are typically grayish-brown and around 15 inches long when fully grown.

The stonefish, the most venomous fish in the world, looks like encrusted rock or dead coral. Most human victims injure themselves when they accidentally step on it. 13 hard spines on its back, sharp enough to puncture rubber soled shoes, carry neurotoxic venom into the wound, causing excruciating pain, temporary paralysis and shock, and in rare cases, even death.

The best way to avoid stepping on stonefishes and scorpionfishes is to shuffle one's feet when wading in shallow waters and to tread lightly while wearing thick-soled shoes. Also, be very careful where you place your hands - the 'rock' you hold on to might be alive!

Crown of thorns

This is the only venomous starfish. It is covered with sharp spines all over its body except on its underside. Its skin contains venom-producing glands which release venom on contact.

Although not fatal, stings are painful, causes redness and local swelling. In some cases, stings may also cause nausea and vomiting. Upon contact, spines may break off and remain embedded.

This starfish can cause widespread damage to coral reefs if their numbers become too large. When that happens, clean-ups are sometimes organized (although such cleanups are widely debated amongst conservationists) where divers collect these starfish (using instruments to avoid hand contact) and then dispose of them on land.

Cone shells

Cone shells are highly sought after by shell collectors due to their attractive and intricate markings. Behind this attractive facade is a highly venomous harpoon which is used to paralyze prey, typically fish, molluscs or worms, before drawing it back to their mouths. The venom is contained in the tongue-like proboscis (radula) equipped with harpoon-shaped teeth. The harpoon can be fired numerous times if needed and with such force that it can pierce wetsuits and clothing. Many human victims get stung when they carry them in pockets or in mesh bags close to the body.

The venom contains neurotoxins which cause weakness and loss of coordination on human victims, affecting the vision, hearing and speech. In severe cases, this can result in respiratory failure and even death. For more information, visit the Cone Shells and Conotoxins site.

Stingrays

Stingrays are shy and frequently hide in shallow waters under rocks, buried under the sand with only their eyes slightly exposed. The tail has a sharp barb near the tip which is used defensively to inflict a painful, venomous sting to any aggressor.

Rays are gentle creatures which is probably why they are commonly found in touch-pools at public marine aquariums. They forage for their food by flapping and uncovering prey hiding in the sandy bottom and never use their sting when hunting. Most human victims are stung around the ankles or feet when they accidentally step on the ray, and fishermen have been known to be stung while sorting out their catch, which includes sting rays, on the boat deck. Although fatalities are rare, they have happened before. In what is probably the most publicised incident involving a stingray, well-known conservationist Steve Irwin, better known as the Crocodile Hunter, died after being stung in the chest by a large bull ray.

As with the stonefish, the best way to avoid stepping on them is to shuffle one's feet when wading in shallow water.

Jellyfish

Jellyfish are not fishes, but are closely related to corals, hydroids and anemones (known collectively as cnidarians which literally means 'stinging creatures'). All possess stinging cells called nematocysts which are used to capture prey. Jellyfish are the free-floating medusa-form of cnidarians, while anemone and coral polyps are the fixed polypoid form.

Jellyfish are composed mainly of water and absorb oxygen directly from the surrounding water. Their tentacles range from 1 cm to 36 metres in length, and contain hundreds of thousands of nematocysts. The bell does not contain stinging cells. Nematocysts can still sting even when the tentacles are severed from the jellyfish so beware of touching jellyfish washed up on beaches or broken tentacles floating in the water.

Most varieties of jellyfish stings are harmless to humans (other than causing painful stings and welts). Of about 2000 known species, only about 70 can seriously harm humans, including the box jelly Chironex, also known as the Sea Wasp, and the tiny Irukandji jellyfish.

The box jelly Chironex fleckeri is the world's most venomous jellyfish and possibly the world's most venomous creature, causing more fatalities than stonefish, cone shells and blue-ring octopus combined. It is found mainly in the northern coastal waters of Australia and in some parts of the Indo-Pacific. It prefers coastal beaches and sheltered inlets and is rarely encountered on coral reefs. Despite its fearsome reputation, green turtles have been observed eating Chironex fleckeri without any problems.

Covering up exposed skin is the best protection against jellyfish.

Hydroids and stinging corals

Fire corals (millepora) and hydroids are hydrozoans, closely related to jellyfish, anemones and other corals. All possess stinging cells called nematocysts, which release thousands of tiny spring-loaded venomous darts upon contact with the skin, causing a painful rash and burning sensation. Despite the pain, stings from fire coral and stinging hydroids are not dangerous unless accompanied by allergic reaction.

Fire coral looks like dead branching hard coral with no visible tissue, mucus or polyps. All species have a characteristic whitish or yellowish tip on each branch and also have a soft, hairy, rounded or fine texture, unlike other hard corals which have a rougher appearance. Most common species of fire coral are typically brown or mustard yellow in colour.

Lace coral looks like hard coral fans with beautiful branches usually adorning ceilings of caves and over-hangs.

Stinging hydroids are commonly found attached to rocks, wrecks, shells, sponges and corals and look like ferns with a central stalk and many side branches. Some crabs, like hermit crabs, and other molluscs may carry hydroids on their shells as a form of protection.

Most cases of stings are caused by accidentally brushing against these stinging corals. As with jellyfish, covering up exposed skin will prevent stings.

The following are some general tips gleaned from medical websites on how to treat victims of stings and wounds caused by the more common hazardous marine creatures. It is not an exhaustive list, nor does it seek to be medically thorough. Links are provided at the bottom of this page to other sites that can provide more detailed information on medical treatment.

Stonefish, ray and urchin wounds

The treatment for wounds from venomous spines typically involve slowing venom absorption and breaking down the venom:

• If possible, elevate the affected area and apply a pressure bandage to slow the absorption of venom in the wound. Do not apply tourniquets as this may cause more damage than it will prevent.
• Immerse the wound in hot water, as hot as you can tolerate, for 30 to 90 minutes to destroy the proteins present in many marine toxins, and to reduce the pain & swelling.
• Control the pain using local anesthetics to prevent shock, since the pain from marine stings can be excruciating.
• Clean the wound with an antiseptic solution and remove spines that are accessible (soaking in vinegar can also be used to dissolve superficial spines). Spines that are deeply embedded may need surgical removal.
• Seek appropriate medical attention for all stings as anti-tetanus medication and antibiotics may need to be administered for infection control, as are antivenins and life support for severe stings.

Jellyfish, fire coral and hydroid stings

The treatment of coelenterate stings (hydroids, jellyfish, fire coral) typically involve deactivation of the stinging cells (nematocysts), followed by removal of any tentacles and management of the injected venom:

• Calm the victim and remove victim from the water to prevent any further contact with the source.
• Do not rub with sand or a towel, and do not pour fresh water which will trigger unfired stinging cells.
• Apply house vinegar (5% vinegar solution) to deactivate the stinging cells, until the stinging stops. DO NOT APPLY ALCOHOL. Vinegar should work with all jellyfish stings except for the Portugese Man of War and Irukandji jellyfish. Note that vinegar does not decrease pain nor does it decrease the effects of the venom - it only prevents the injection of more venom by disabling undischarged nematocysts from firing.
• Remove tentacles with a gloved hand or tweezers to keep from getting stung, then rinse with more vinegar or salt water.
• Apply a paste or solution of meat tenderizer, if you have it, to neutralize the venom.
• Use analgesics to relieve pain, or if these don't work, try icepacks or cold vinegar.
• Dry the skin and apply hydrocortisone ointment and take a diphenhydramine preparation (like Benadryl) for mild allergic reactions.

Note that in all of the above cases, watch out for any life-threatening reactions like spasms, shock and breathing difficulty. If these are present, seek emergency medical attention immediately.

For more information on dangerous marine animals and first-aid information, try these links: