Jacques Cousteau escaped a near-fatal car crash, invented the aqualung and founded modern marine conservation – all in a day's work for a man who believed that "the impossible missions are the only ones which succeed". Cousteau will always be remembered as the man who brought marine life to cinema and television screens for the first time. Along with the crew of his iconic ship, Calypso, he inspired a generation of children to become scientists and pioneered marine conservation at a time when conservation of the land – let alone the sea – had scarcely been thought of. Yet in later life this iconic figure argued that the human population should be restricted to 100,000 for the sake of the environment, and following his death his family have disagreed about how best to continue his work. In this, Cousteau's centenary year, naturalist Bridget Nicholls tracks down friends, colleagues and family members to tell the story of this often difficult – occasionally impossible - but always inspiring man.
BBC
First broadcast on 19 November 2010.
Thus the paralyzing neurotoxin in puffer fish results from their diet rather than chemical processes within the fish. However, because puffer fish target tetrodotoxin specifically and amasses the toxin within their internal organs, this process can be defined as a defense mechanism.
Of the phylum Mollusca and class Gastropoda, cone snails 15cm long are beautiful, seemingly innocent, yet potentially deadly animals. Found typically in shallow Indo-Pacific waters, most of these predatory marine snails have a highly developed venom apparatus. There are over 500 species, and 18 have been known to be dangerous to humans. The cone snails that eat fish (as opposed to other mollusks or worms) are most dangerous to people, as we are also vertebrates. Fortunately, the snails are nocturnal, burrowing in the sand and coral during the day and coming out at night to feed. The snail has four protrusions: a siphon for respiring, two eyestalks to sense prey, and a proboscis to inject venom. The toxins are produced in the venom duct, which can be over seven times the length of the snail itself.
The duct is attached to the venom bulb that contracts to push the venom through the harpoonlike ‘tooth’. These teeth that may reach up to 1cm in length are modified hollow radular teeth, made in the radular sac. The proboscis still attached to the snail by a thread impales the fish, immediately paralyzing it. The snail proceeds to retract the thread and engulf the prey through its radular opening into its stomach.
The active components of the venom are small peptides of 12-35 amino acids in length. Due to the high density of disulfide bonds, these conotoxins are highly constrained. Different toxins block different ion channels in the nervous system, stopping chemical signals from traveling. This halt in communication causes paralysis in the fish victims. Three paralytic toxins seem to be the main focus: alpha-, omega-, and mu-conotoxins. The A-superfamily, including the -conotoxins and the A-conotoxins, binds to and inhibits the nicotinic acetylcholine receptor. The O-superfamily, including -conotoxins, the -conotoxins, the O-conotoxins, and the -conotoxins, decimates the release of acetylcholine through the prevention of voltage activated entry of calcium into the nerve terminal. The M-superfamily (-conotoxins) directly inhibits muscle action by binding to the postsynaptic sodium channels. Cone snails are able to produce hundreds of conotoxins, creating a lethal combination of one of two kinds of paralysis: excitotoxic shock (all muscles contracted at the same time: rigid) or flaccid paralysis (no muscles contract: limp). The venom of these snails can cause a variety of symptoms on humans. Mild stings usually on the hand initially resemble a bee sting, followed by numbness around the sting. More serious stings can cause partial paralysis and respiratory and cardiac failure. Weakness, nausea, and loss of coordination, hearing, vision, and/or speech are also common. At least two species (Conus textile and Conus marmoreus) have been known to kill humans. Unfortunately there is no antitoxin for cone snail venom; researchers have, however, begun to find that the venom could be used for forms of painkillers such as morphine, but would not have the side effects of addiction.
The Stonefish, scientifically known as the Synanceia verrucosa, is a small marine fish native to the Indo-Pacific. The stonefish can be found from as far west as the East Coast of Africa to as far east as French Polynesia. Few people have probably seen a Stonefish in person. They sometimes show up in personal aquariums or in sushi restaurants in eastern Asia.
Here's a map of the distribution of the Stonefish:
The Stonefish makes its habitat in the shallow waters of coral reefs. The Stonefish received its name because of its brownish color that helps it to camouflage itself among rocks and coral. Stonefish are very small (30-40 cm) and therefore their prey usually consists of other small fish as well as shrimp, while their primary predators are sharks and stingrays. Stonefish feed by camouflaging themselves next to rocks and staying very still. When prey venture too close, they strike with a surprising amount of speed. Their ability to camouflage is a huge help in their hunting and their ability to hide from predators.
Here's a camouflaged Stonefish:
The stonefish is debatably the most venomous fish in the world. However, they are not aggressive creatures as they only release their venom as a defense mechanism. In fact, it’s an involuntary reaction to detected pressure. When a predator such as a shark or a human foot comes into contact and applies pressure on a Stonefish, it’s thirteen dorsal spines extend (as seen in the video) from it’s back and transfer venom into its victim. After a stonefish uses its venom, it must wait a period of a few weeks until more venom is produced and ready to be utilized. The venom of the Stonefish is extremely dangerous. The venom is called verrucotoxin or VTX. It is a mixture of several protein-based venoms such as stonustoxin, cardioleputin, and trachynilysin. Scientists aren’t quite sure how the venom actually works. Contact with Stonefish venom is extremely painful and comes with dangerous health implications. The severity of the injury depends on how deep and how many of the venomous spines reach into the victim. The venom can cause “respiratory weakness, damage to the cardiovascular system, convulsions and paralysis” In serious cases, Stonefish venom can lead to death. Luckily, there is antivenom. If medical attention isn’t reached within a couple of hours of the injury, there is a serious risk of fatality. Survivors of stonefish encounters often times suffer from nerve damage as well as joint and muscle pain in the areas surrounding the spines entrance point. Thankfully, encounters with the Stonefish are rare and there are very few fatalities each year.
Here's a video of Steve Irwin extracting venom from a Stonefish:
