The enormous starry pufferfish, Arothron stellatus markings are bold and startling in the cobalt hue of the water. The pufferfish is curious and unthreatened by a divers presence sailing slowly but deliberately along the reef.
World’s Most Poisonous
There are around 189 pufferfish species worldwide, while many inhabit estuarine environments, they are found mainly in the tropical and subtropical waters of the world. The enigmatic sailor before us was at the upper end of the size, but these fish range from a diminutive 2.5 cm dwarfs to a giant 1-metre long. Their dubious claim to fame is that they are considered the second most poisonous animal in the world, after the golden poison frog. And they have one of the most extraordinary range of anti predator adaptations in the ocean.
Markings on fish are used for many reasons; such as camouflage or warnings and pufferfish are often decorated in boldly marked advertising; the message to any would be predator is loud and clear; “I’m toxic so back off”. And the magnificent starry puffer before us uses this tactic. Others go for concealing themselves as a defense and disappear quickly into the framework of the reef.
The “danger” advertising of pufferfish is used by other fish in what is known to biologists as “Batesian mimicry”. This is where an edible species evolves to look similar to an inedible species to avoid predation.
In this case the juvenile filefish, Canthigaster valentine, accurately mimics the unpalatable pufferfish, Paraluterus prionuru,s and thereby vastly increases its chances of survival in the hostile environment of a coral reef.
Pufferfish tend to be slow moving creatures but they are highly maneuverable, combining use of their pectoral, dorsal, caudal and anal fins to maximum effect. The bursts of speed required in an quick escape, is made possible by their tail fin, which is used as a rudder. But a pufferfish’s first line of defense against attack is its outstanding eyesight, much like humans. And it is only when this has failed that they move to the next stage; inflation. A predator unlucky enough to gulp a pufferfish can get a nasty shock as the pufferfish’s spines puncture its mouth or, the now massively inflated ball, chokes them to death.
Your average pufferfish have the astounding ability to transform themselves to several times their normal size. They can do this by ingesting huge amounts of water, and sometimes air if they are out of water, into their highly elastic and distensible stomachs.
Now if the predator survives spines and inflation, just throw in a respectable dose of the deadly tetrodotoxin, a poison that is fatal for many animals and 1200 times more deadly than cyanide, and you have the warship to end all warships. Concentrated in the liver, ovaries and skin of the pufferfish, it is thought that this toxin is a product of the bacteria from the food they eat (mainly crustaceans, bivalves, echinoderm and an assortment of other invertebrates).
Fish farmers have produced puffers without toxins by controlling their diets. The gastric contents of shellfish are believed to be the culprit in producing the pufferfish’s deadly cargo. Their high tech arsenal makes them a formidable adversary to any would be predator. Although for some of the seas more dangerous predators, such as tiger sharks and sea snakes, if they can get past the inflation and the spines, they have a tasty snack. Bizarrely they seem immune to the lethal toxin.
Tetrodotoxin is fatal to humans, there is estimated to be enough toxin in an average puffer fish to kill thirty adults.
The meat of some pufferfish, called Fugu in Japan, is commonly eaten in Japanese cuisine. Its consumption is a cause of a number of deaths annually, where the meat has not been correctly prepared. The toxin completely paralyses the victim while they remain conscious, even paralysing the breathing muscles. And there is no known antidote. It is also thought that the poison from pufferfish must be used in the practice of voodoo to produce the “zombie” legends.
Although pufferfish are not currently listed as threatened, there is concern about their use for the fugu trade as well as their capture for curios in Asia, where puffers are dried and made into ornaments, and their capture for the aquarium trade.