Family Diodontidae
Balloonfish and Porcupinefish
Class: Actinopterygii (ray-finned)
Order: Tetraodontiformes
Key Features:
Ballonfishes and porcupinefishes possess two fused front teeth in their beak and in most species demonstrate exceptional abilities to self-inflate. Often lacking toxic skin compounds, many species instead are covered in strong erectile spines. Sucking water into a ventral diverticulum of the stomach facilitates inflation. Often slow moving they are often encountered by scuba divers along rocky overhangs, ledges, and nestled between rocks.
Notable Species in the Sea of Cortez
- Diodon holocanthus
- Balloonfish
- Diodon hystrix
- Porcupinefish
- Chilomycterus reticulatus
- Pacific Burrfish
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Diodon holocanthus
Balloonfish
Isla San Pedro Nolasco
San Carlos, Sonora, Mexico
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Family Diodontidae
Balloonfish, Porcupinefish, and Burrfish (Peces erizos)
Commonly referred to as puffers, members of the family Diodontidae are in fact very dissimilar from the true puffers. More correctly termed porcupinefishes and balloonfishes, the diodonts are significantly better at inflating themselves and are often able to inflate into a nearly perfect round ball. They also lack the neurotoxic tetrodotoxin secretions of pufferfish but make up for this shortcoming by the presence of many long sharp spines. These spines become erect when the fish inflates. Although tetrodotoxin may be lacking, many species nevertheless secrete toxic or irritating skin compounds.
There are nineteen species contained in six genera worldwide. The Sea of Cortez is home to three species of porcupinefishes in two genera. The most common species within the Sea of Cortez is the ballonfish, Diodon holocanthus. This is a common species throughout the Gulf and is in fact circumtropical in distribution. While common in most areas of the Sea of Cortez, it decreases in abundance in the northern Gulf. A comical fish and a generally poor swimmer, ballonfish are tempting targets for scuba divers to capture and inflate. Such behavior is not encouraged as this places undue stress on the animal and also predisposes the fish to bacterial infections caused by the loss of their protective mucous layer. While not generally fatal, many ballonfish bear the scars of such infections, often in the region surrounding the caudal peduncle or the forehead.
The other species of Gulf porcupinefish that displays long erectile spines over the bulk of its body is Diodon hystrix. Diodon hystrix may be differentiated by the presence of longer spines behind the pectoral fin and shorter spines on the forehead. In D. holocanthus, the forehead has longer spines. In addition, D. holocanthus has a dark bar over the eyes and four dark saddles whereas D. hystrix is more evenly colored, with only small spots rather than any dark bars. D. hystrix also reaches a greater maximum size than D. holocanthus. The third species in the Sea of Cortez, is the pacific burrfish, Chilomycterus reticulates. Uncommon in the Sea of Cortez, this species lacks erectile spines and instead has short immobile three-based spines.
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