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Considered to be one of the most unusual in appearance of all fishes in the ocean is the puffer. From the Tetraodontiformes order, the puffer family of fish are distinguished by their round, plump bodies which have given them such common names as blow fish and swell fish. Most amazingly, the puffer fishes have a somewhat thick, leathery, skin that does not have scales, but has tiny spines set deeply in the pores. When the puffer fish is calm, these spines remain unseen. But at the instant a predator approaches, the spines immediately become visible as the puffer fish causes its body to swell. This is another of the very interesting distinguishing characteristics of the almost one hundred species of the puffer fishes. When predators approach or a threatening situation arises, the puffers become highly agitated, filling a special sac found inside their body with air or water. This inflation causes the fish to take on a balloon like appearance with all its tiny spines fully extended. Although most puffer fish are small at around three to twenty inches; some species reach an incredible size of up to three feet, which makes their swollen condition quite a sight to see. Most puffer fish prefer to make their home in warm coastal waters but an occasional species can be found fresh or brackish water.
The puffer fish have an ancient lineage that dates back through the centuries. It is believed that this fish once had the same appearance as the sunfishes eventually evolving to an appearance that is more like the family of perch and especially the surgeon fish who are their known as their ancestors. Today the puffer fishes have a single dorsal fin that is opposite the anal fin. They have no pelvic fins and are able to move only by moving their actively moving the dorsal and anal fins. They are able to inflate their bodies by taking in great gulps of water or air in a matter of just seconds, which is done at the surface of the water. Puffers are able to initiate this amazing feat because they have a type of sac that is attached directly to the intestines by cartilage like strands or is actually a part of viscera. Once they close off their stomach and esophagus with a type of muscular valve, the fish then uses it specially formed gills as a suction pump to inflate the sac. Since puffer fish have no ribs or pelvic bones they are capable of tremendous expansion. But to keep them from blowing up too large, these amazing fish also have controls in their skin muscles that regulate their expansion.
Once the puffer fishes body is swelled, most predators have a difficult time gripping the body or biting into it. In fact, the tough outer body of this fish has been known to remain undamaged after being stood on by a grown man. In most cases the puffer fish uses water to expand its body since water is the easier of the two elements to eject. This is done by the release of the muscular valves that allows the water to escape through the gill openings and mouth. Puffers rarely are known to use air as a means of expanding their bodies simply because the only way to release it is in small increments through the gills. Since the teeth on many species of the puffer fishes are fused together much like the beak of a parrot, these species tend to feed on such hard shell creatures as mollusks, clams, crabs, snails, sea urchins and other crustaceans. In some species the adults are known to poisonous due to the tetraodontoxin that is found in large concentrations in their organs. Even though this highly toxic substance is known to cause death many of these species are still eaten in some areas of the world. Most species of male puffer fish are highly territorial showing extreme aggression when faced with another male of their species. Males have even been observed puffing up to appear larger when larger males appear in an attempt to scare them away.
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