Wednesday, June 24, 2009

Description & Behavior

The balloonfish, Diodon holocanthus (Linnaeus, 1758), aka balloon porcupinefish, blotched porcupine fish, blotched porcupine, brown porcupine fish, fine-spotted porcupinefish, freckled porcupinefish, freckled porcupinefish, hedgehog fish, long-spine porcupinefish, porcupine, porcupinefish, spiny balloonfish, and spiny puffer, is known for its large eyes, spines and it's ability to swell like a balloon when attacked. This comical species reaches between 20-35 cm, and reaches a maximum of 50 cm. There are a total of 13-15 dorsal and anal soft rays. Juveniles have spots on the ventral side, adults have dark blotches and spots on the dorsal side. There are 14-16 spines between the snout and dorsal fin. A large brown bar is found above and below each eye; and a broad transverse brown bar on occipital region, or upper surface of the back of the head.
The body of the balloonfish is covered in long, sharp spines that extend when the fish inflates by taking in water. All members of the Family Diodontidae are capable of inflation, and may also change in color when threatened.
World Range & Habitat
Circumtropical in distribution. These fish are found in the Western Atlantic from Florida, USA to the Bahamas and Brazil, in the Eastern Atlantic around 30°N-23°S, and in South Africa. In the Eastern Pacific from Hawaii to Pitcairn and the Easter Islands, and from southern California, US to Colombia and the Galápagos Islands. They are reef fish with a depth range of 2-100 m.
Feeding Behavior (Ecology)
Balloonfish are nocturnal predators, generally hiding in crevices in the reef during the day. The teeth are fused forming a strong, beak-like mouth for consuming snails, sea urchins, and hermit crabs. These fish are relatively poor swimmers. Juveniles are consumed by pelagic predatory fishes such as tuna and dolphins. Adults fall prey to sharks.

Life History

Reproduces via dioecism (sexes are separate), fertilization is external with a spawning frequency of one clear seasonal peak per year.
The balloonfish has a pelagic life stage. Spawning occurs after males slowly push females to the surface. The eggs are buoyant, hatching after approximately 4 days. The larvae are well developed with a functional mouth, eyes, and a swim bladder. They are predominately yellow with scattered red spots, and are covered with a thin shell until they are about 10 days old, after which the shell is lost and the spines begin to form. Approximately 3 weeks after hatching, the fins and fin rays are present and the teeth are formed. As juveniles, they develop their olive to brown color with dark spots appearing on the ventral side that serve as camouflage for juveniles floating in Sargassum weed. The spotting is retained until the juveniles move inshore and become adults.

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