Facts About The Inflatable Swell Shark

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The swell shark is able to inflate itself to twice its normal size by swallowing large amounts of water.

The swell shark, scientifically known as Cephaloscyllium ventriosum, is a species of shark unique in its ability to inflate itself to twice its normal size by engulfing large quantities of water when confronted as a way of intimidating a potential predator or tucking itself in a crevice firmly enough, making it all the more daunting to pull it out. Said ability to swell up one’s own body is normally associated in the natural world to the puffer fish found normally in Japanese waters and as the island’s exotic trademark dish.

swell shark

The swell shark

The swell shark is observed to grow to about 1 m in body length. It is found normally in the eastern Pacific from central California to the Gulf of California and southern Mexico within depths of reportedly up to 457 m, overlapping with the local population of leopard sharks, with whom swell sharks are sometimes easily confused, seeing that both sharks display distinct markings on their bodies.

The swell shark is a nocturnal hunter, as it would hide itself away from the outside world in reef crevices during the day and only emerge during the night to ambush their prey, such as bony fish, mollusks and crustaceans. The swell shark expresses two different methods of feeding: by either expanding its gills and oral cavity to produce a large vacuum, with which it uses to suck in prey; or by simply lying in wait for unwitting prey to swim into its open maw. Due to a large oral cavity, the swell shark is capable of engulfing larger prey as well. The swell shark also exhibits a huge number of rows of tiny pronged teeth which facilitates the task of gripping firmly on to its prey, especially those with slime-coated bodies.

The swell shark is oviparous, meaning its eggs do not undergo any embryonic development within the mother shark, which lays them out to be fertilized by the male parent with a sperm in a process called external fertilization. The female swell shark tends to produce a substance which surrounds an egg going through the oviduct, giving rise to a protective shell around the egg. The swell shark’s egg cases, or egg capsules, containing the shark’s fertilized eggs would initially appear malleable and pallid, only to transform within a few hours into hard brown casings after birth. Said egg cases are normally found on reefs and the eggs they contain hatch only after around 7 to 10 months, with the water temperature being a major factor in this situation. Young swell sharks usually measure at around 6 inches in body length. They are observed to implement bony protrusions found on its back known as denticles to free themselves from the egg cases. Upon hatching, swell shark pups are immediately capable of eating prey such as small mollusks and crustaceans.

swell shark in its hiding spot

The swell shark in its resting place

Though swell sharks are not subjects to poaching activites, they are usually caught alongside lobsters and crabs unintentionally, which is seen as a threat to the swell shark population, what with its low rate of reproduction and limited number of pups born yearly. It should be noted here that swell sharks do not pose as a considerable threat to people and would only bloat up whenever confronted.



1. http://www.aasharks.com/types-of-sharks/swell-shark.htm

2. http://marinebio.org/species.asp?id=383


Posted on Feb 13, 2011
Phoenix Montoya
Posted on Feb 11, 2011