The stonefish's lifestyle makes this, the most venomous fish in the world, particularly dangerous to unwary humans. Lying on the seabed, looking exactly like an encrusted rock, it waits for small fish and shrimps to swim by and then, with lightning speed, opens its mouth and sucks them in. The whole ambush has been timed at just 0.015 seconds.
Vulnerable to bottom-feeding sharks and rays, it has developed a defence - a row of unlucky 13 venomous spines along its back. It is, in fact, the victim who injures him/herself. Each stonefish spine is encased in a sheath containing bulging venom glands. Downward pressure on the spine causes the sheath to be pushed back, the venom from the pressurised glands shooting forcefully up grooves on the surface of the spine into the deepest part of the wound. (It takes a few weeks for the glands to regenerate and recharge.)
Victims become frantic with pain which lasts for hours. Temporary paralysis, shock and even death may result. Stonefish may be found from exposed sand and mud in tidal inlets to depths of 40m. Prevention involves wearing thick-soled shoes and treading gently - spines may penetrate soles if a stonefish is jumped on. Also, take care when turning over 'rocks'.
Sea snake venom is more toxic than that of land snakes, however these animals pose little risk. Most are shy and stay away from people, biting only when provoked, if at all. Even then they tend not to use their venom.
It is reserved for quickly immobilising prey, not for defence. In fact, about 65% of bites are 'blanks'. Nevertheless, the potential danger of a sea snake should not be underestimated and they should be treated with respect.
Sea snakes are air breathers probably descended from a family of Australian land snakes. They inhabit the tropical waters of the Indo-Pacific and are highly venomous. Thirty-two species have been identified in the waters about the Barrier Reef in Australia. They seem to congregate in certain areas in the region about the swain Reefs and the Keppel Islands, where the olive sea snake (Aipysurus laevis) is a familiar sight.
Sea snakes have specialized flattened tails for swimming and have valves over their nostrils which are closed underwater. They differ from eels in that they don't have gill slits and have scales. Due to their need to breathe air, they are usually found in shallow water where they swim about the bottom feeding on fish, fish eggs and eels.
The yellow-bellied sea snake ( Pelamis platurus ) is planktonic, and is seen on occasions floating in massive groups. Fish that come up to shelter under these slicks provide food for the snakes. Occasionally these yellow-bellies get washed up on beaches after storms and pose a hazard to children.
Aggressive only during the mating season in the winter, the sea snake is very curious, and they become fascinated by elongated objects such as high pressure hoses. Advice here is to inflate your BC so as to lift away from the bottom and the snake. Provoked snakes can become very aggressive and persistent --requiring repeated kicks from the fins to ward them off.
Persistent myths about sea snakes include the mistaken idea that they can't bite very effectively. The truth is that their short fangs (2.5-4.5mm) are adequate to penetrate the skin, and they can open their small mouths wide enough to bite a table top. It is said that even a small snake can bite a man's thigh. Sea snakes can swallow a fish that is more than twice the diameter of their neck.
Most sea snake bites occur on trawlers, when the snakes are sometimes hauled in with the catch. Only a small proportion of bites are fatal to man, as the snake can control the amount of envenomation, a fact probably accounting for the large number of folk cures said to be 95% effective.
Intense pain is not obvious at the site of the sea snake bite; 30 minutes after the bite there is stiffness, muscle aches and spasm of the jaw followed by moderate to severe pain in the affected limb. There follows progressive CNS symptoms of blurred vision, drowsiness and finally respiratory paralysis. A specific antivenin is available; if not obtainable-the Australian tiger snake antivenin or even polyvalent snake antivenin can be used.
