The balloon fish is a boxy-looking species with an angular head and large eyes. In its normal, nonthreatened pose, the long spines (modified scales) on its skin lie fl at against its body. The pectoral and tail fins are small and delicate. The skin is pale, and there are dark blotches on its skin, giving it a mottled look. Fully grown, the balloon fish can reach lengths of 50 cm.

The balloon fish is associated with tropical coral reefs, mangroves, sea grass beds, and rocky seabeds. It can be found around the world. In the Atlantic, it is found from the Bahamas to western Brazil, and in the Pacific, it is distributed widely through the numerous island groups. It is a shallow water species, rarely venturing to depths of more than 100 m.

• The balloon fish is a type of porcupine fish, of which there are 19 species. They are closely related to pufferfish, which have a similar defensive ability, but not quite as pronounced.

• The internal organs of these fish, such as the ovaries and liver, contain a potent toxin known as tetrodotoxin, which is at least 1,200 times more poisonous than cyanide.

• It acts on the nerves, disabling their ability to transmit electrical signals. Tetrodotoxin is produced by several types of bacteria dwelling inside the fish. Interestingly, the bacteria are somehow obtained from the fish’s diet. Fish bred in captivity are not poisonous.

• In the Far East, especially Japan, the flesh of the pufferfish and its relatives is a rare delicacy. The term fugu is applied to both the fish and its meat. As food, the meat of these fi sh requires very careful preparation by very experienced chefs. The toxin is not damaged by washing or cooking, and an ill-judged fi lleting or misplaced slice can easily cause the accidental, fatal poisoning of a fugu lover.

• A drug called tectin has been developed from tetrodotoxin, which shows great potential as a powerful pain reliever that is able to dull the discomfort of cancer and drug withdrawal.

• The balloon fish and other types of porcupine fish are also fond of nibbling coral to extract the succulent polyps within. The calcium carbonate skeleton of the coral is swallowed, and some fish have been caught with over 500 g of the crushed material in their stomachs.

• For reasons that are not yet understood, the pufferfish and it skin have the smallest genomes of any known vertebrate. Their complement of DNA appears to have little of the surplus carried by other species.

• Even out of water these fish can inflate themselves quite happily using air, but due to the diff erent properties of air and water, they have difficulty deflating themselves and can only do so if returned to the water.

• In the Far East, the dried, inflated bodies of these fish are often made into curios or bizarre lanterns illuminated from the inside by an electric bulb. The Pacific islanders once used the dried, swollen bodies to make fetching ceremonial helmets.