Porcupinefish Swim-bladder
Diodon species
Porcupinefish Swim-bladder (Diodon species), Wild Guide to Moreton Bay
These strange leathery objects found occasionally on beaches are special internal organs of the Porcupinefish. They were once the swim-bladders that inflated or deflated to control buoyancy and balance as the fish moved up and down in the water. Although many fishes have swim-bladders they are generally soft and decay quickly, whereas those of the porcupinefish are very tough and survive for a long time after the fish has died. In life when agitated the porcupinefish can inflate its body and wedge itself into the reef, making it nearly impossible to swallow by a predator.
Porcupinefish are found throughout the Indo-west Pacific region, with ten species known from Queensland.
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