Balloonfish

The balloonfish or Diodon holocanthus is a bony fish that can be described as a football with a tail ("Balloonfish (Spiny Porcupine Fish)"). This tail or caudal fin, is also rounded ("Balloonfish"). As for coloration, the balloonfish has a tan body with brown blotches and black spots over the entire length ("Balloonfish"). Additionally, the balloonfish has a brown band that runs over its forehead, from eye to eye ("Balloonfish"). The eyes of the balloonfish are large and pronounced with yellow irises and its protrusive lips are supported by large, fused, front teeth that form a beak-like structure ("Balloonfish (Spiny Porcupine Fish)"). The balloonfish has long spines that are found over the entire body and these fish range in length from 20-35 cm ("Balloonfish (Spiny Porcupine Fish)"). However, they can grow to 50 cm ("Balloonfish (Spiny Porcupine Fish)").

Image of a balloonfish showing his colorations and body shape (http://www.ryanphotographic.com/diodontidae.htm).

As for the geographical distribution of the balloonfish, it can be found in circumtropical areas ("Balloonfish, Diodon holcanthus"). That is, these fish are found in the Western Atlantic from Florida to the Bahamas and Brazil, in the Eastern Atlantic, and in South Africa ("Balloonfish, Diodon holcanthus"). These fish are also found in the Eastern Pacific from Hawaii to Pitcairn and the Easter Islands, and from southern California to Colombia and the Galapagos Islands ("Balloonfish, Diodon holcanthus"). Balloonfish are reef fish with a depth range of 2-100 m ("Balloonfish, Diodon holcanthus"). That being said, I observed the balloonfish on a patch reef called Coffin’s Patch.

            One very unique characteristic of the balloonfish is that it is able to inflate. When inflated, the spines that usually lie flat, will stick out straight. This helps ward off predators by making the balloonfish look larger as well as making the balloonfish difficult/painful to eat. The inflation is accomplished by the balloonfish swallowing air or water ("Diodon holoanthus: Blotched porcupine"). Once ingested, the air or water enters the expandable stomach ("Diodon holoanthus: Blotched porcupine"). In addition to the stomach, the skeletal structure of the balloonfish aids in the inflation process ("Diodon holoanthus: Blotched porcupine"). That is, the balloonfish lacks pleural ribs and a pelvic girdle ("Diodon holoanthus: Blotched porcupine"). It also has a very flexible vertebral column ("Diodon holoanthus: Blotched porcupine"). The skin of the balloonfish facilitates inflation as well. The skin is highly elastic because of microfolds in the epidermis and collagen fibers in the dermis ("Diodon holoanthus: Blotched porcupine"). This allows the balloonfish to extend up to 40% of its initial length ("Diodon holoanthus: Blotched porcupine").

Image of a balloonfish inflated with the spines sticking out (http://www.radiotimes.com/uploads/images/Original/28894.jpg).

            Diodon holocanthus reproduce via dioecism and external fertilization ("Balloonfish, Diodon holcanthus"). They spawn during one clear seasonal peak per year ("Balloonfish, Diodon holcanthus"). Spawning occurs in late spring and early summer after the males slowly push females to the surface ("Balloonfish, Diodon holcanthus"). The eggs are buoyant and hatch after approximately 4 days ("Balloonfish, Diodon holcanthus"). The larvae are well developed with a mouth, eyes, and a swim bladder ("Balloonfish, Diodon holcanthus"). They are mostly yellow with scattered red spots, and are covered with a thin shell until they are about 10 days old ("Balloonfish, Diodon holcanthus"). After the shell is lost, the spines begin to form ("Balloonfish, Diodon holcanthus"). About 3 weeks after hatching, the fins and fin rays are present and the teeth are formed ("Balloonfish, Diodon holcanthus"). As juveniles, balloonfish develop their olive to brown color with dark spots appearing on their ventral side ("Balloonfish, Diodon holcanthus"). These dark spots serve as camouflage for juveniles that float in Sargassum ("Balloonfish, Diodon holcanthus"). The spotting is maintained until the juveniles move inshore, settle, and become adults ("Balloonfish, Diodon holcanthus").

          Ecologically, balloonfish are nocturnal predators, usually hiding in crevices in the reef during the day ("Balloonfish, Diodon holcanthus"). The balloonfish use their beak-like structure to consume snails, sea urchins, and hermit crabs ("Balloonfish, Diodon holcanthus"). These fish are relatively poor swimmers and juveniles are consumed by pelagic predatory fishes such as tuna and marine mammals such as dolphins ("Balloonfish, Diodon holcanthus"). On the other hand, adults tend to fall prey to sharks ("Balloonfish, Diodon holcanthus").

            As for the conservation of the balloonfish, I was unable to find any current efforts. This is due to the balloonfish being of least concern according to the IUCN Red-List of Threatened Species. The species appear to be common and do not have any major threats ("Diodon holocanthus").