Anatomy and Physiology

Members of the Tetraodontidae family generally share the same shape and general characteristics.  Pufferfish generally exhibit a torpedo-shaped body with a somewhat anteriorly placed dorsal fin containing 7-18 soft rays.  The anal fin is situated ventrally, in line with the dorsal fin and containing approximately 7-18 soft rays. The caudal fin is either moderately forked or rounded.  Pectoral fins are found just behind the gills.   Teeth are fused in a powerful jaw with a median suture apparent at the midline, appearing as 4 fused teeth (hence tetraodontidae, meaning four teeth).  This is of particular use in crushing the shells of mollusks and crustaceans.  The eyes of pufferfish are somewhat large for its body, and are capable of moving independently.  These fish have smooth bellies, or in some cases, backward pointing spines ventrally.  Click the first picture to download and view a short movie of this figure-eight puffer swimming in its tank.  Note the dorsal and anal fins as its primary source of propulsion, along with its pectoral and caudal fins, which are primarily used as rudder. (movie courtesy of Keith L. Jackson)

Perhaps the most distinctive visible characteristic is the fact that Tetraodontidae can inflate their bodies with water when threatened.  This is accomplished by the use of an oral valve located on the floor of their mouth.  Let's let a real expert explain this amazing process.  The following excerpt is taken from "When Fish Bite", an article by Frank Stephenson for "Research and Review".
"In studying the feeding behavior of the Tetraodontiformes, the group of fishes to which the puffer belongs, Dr. Peter Wainwright stumbled upon the secret to the fish's bizarre attribute-a special oral valve attached to the floor of its mouth.  Scientists who had previously noted the organ's presence had speculated that it played some part in inflation, but couldn't pin down what that might be. Wainwright has been able to explain the organ's vital role and also to show how the whole process works. After filling its mouth with water, the fish flexes a large muscle at the base of the oral valve which then catapults forward against the entire front of the mouth, forming a tight seal against the back of the front teeth. This prevents the water from escaping while a "plunger" type of apparatus -a mechanism driven by a highly modified gill arch called a branchiostegal ray-mounted at the base of the throat forces the water upward where it shoots down the fish's esophagus and into its stomach. Using a series of electrodes embedded in the puffer's head muscles, Wainwright learned precisely which muscles are involved and how they fire in rapid sequence to accomplish the task. The trick doesn't stop there, of course. Scientists have long known that puffers have stomachs and skin of unparalleled elasticity. Unimpeded by ribs (puffers don't have them), the fish's water- (or air-) filled stomachs are thus free to balloon, making their owners a difficult mouthful indeed for any passing predator."

These amazing fish don't stop there, however.  Most people have heard of "fugu", which is actually a prepared Japanese dish using the Fugu Puffer as the main constituent.  Those of you who familiar with fugu have undoubtedly heard of fugu poisoning.  One of the most powerful poisons in the world is present in many pufferfish.  The poison is called "Tetrodotoxin".  This is such an interesting subject, it has been given its own page on this site.  Click the link below to continue to this subject.

>>click here to continue to The Poison Tetrodotoxin>>>>>>>>

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