Pufferfish Tetraodon hispidus
The blowfish, swellfish, balloonfish or pufferfish is a fish of the family Tetraodontidae (order Tetraodontiformes) named after its ability to inflate itself to several times its normal size by swallowing water or air when threatened. The same adaptation is found in the related porcupinefish, which also have spines.

Pufferfish accumulate the poison Tetrodotoxin from a symbiotic bacterium, which makes them highly poisonous even to humans. Despite this they are prized as a delicacy in Japan, where fugu (河豚 or フグ) is carefully prepared by removing the poisonous skin and organs and served as sushi or sashimi, or cooked in broth. In recent years, most fugu is produced from farmed pufferfish, where the bacterium is rare, and so the resulting fish are generally not poisonous.

Apparently due to some unknown selection pressure, intronic and extragenic sequences have been drastically reduced within this family. As a result they have the smallest known genomes among the vertebrates, while containing a genetic repertoire very similar to other fishes and thus comparable to vertebrates generally. Since these genomes are relatively compact it is relatively fast and inexpensive to compile their complete sequences, as has been done for two species (Fugu rubripes and Tetraodon nigroviridis).

The Blowfish encryption algorithm is named after the blowfish.

External Links