Threetooth puffer

The name Triodon macropterus comes from the Ancient Greek τρι- (tri-, meaning 'three') and ὀδούς (or ὀδών, odoús, odṓn, meaning 'tooth'), and refers to the three fused teeth that make up a beak-like structure.[2]

The threetooth puffer is native to the Indo-Pacific, where it is found mainly around Australia and off the coast of Asia at depths from 30–300 m (98–984 ft).[2][4][5][6][7] Its habitat is pelagic, consisting of continental shelves, slopes, seamounts, and knolls.[8][7]

Little is known about the diet of the threetooth puffer. However, a dissection of the stomach of a caught juvenile specimen uncovered traces of mysid crustacean, foraminifera, echinoids, and sponges.[9]

The intestinal tract of the threetooth puffer (the esophagus, stomach, and intestines) is lined with several papillae, protrusions of the gut lumen.[9] After the stomach, the tract branches off into a specialized sac-like compartment called Tyler's Pouch.[9] Within the Tyler's Pouch the papillae are much larger in size and number compared to those prior.[9] The role and function of Tyler's Pouch is largely unknown.[9]

The threetooth puffer reaches a maximum length of 54 cm (21 in).[5] Its body is yellowish-brown with a white belly flap as large as or larger than its body which it inflates with seawater when threatened.[2] The flap is inflated by rotating the shaft-like pelvis downwards, exposing a black eye-spot contoured with yellow.[3][4][10] This makes the animal appear much larger to predators, and less likely to be eaten.[3] When danger is not present, the flap is retracted seamlessly into the body and the eye-spot is not visible.[2]

The head of an adult threetooth puffer makes up approximately 30.6% of the length of its body, and the eyes make up about 7.5% of its body length.[9] The upper jaw is composed of two dental plates while the teeth on the lower jaw protrude from a single dental plate, resulting in a beak.[2]

The threetooth puffer has ribs, a beak, and no pelvic fins which are all characteristics of tetraodontiformes.[7]

Adult scales have a rhombic base, and each has a median ridge from which several spines protrude.[9]

• 
  Living specimen, belly flap half extended
• 
  Desiccated museum specimen
• 
  Illustrated specimen by Cuvier
• 
  Eye
• 
  Beak-like structure composed of fused teeth
• 
  Lateral eye-spot

The smallest Triodon macropterus specimen on record measures 20mm long and belongs to the ichthyological section of the Muséum Nationale d'Histoire Naturelle in Paris.[9] The head of the specimen makes up 45% of the length of its body, and its eyes make up 18% of its body length.[9] As a juvenile, the pelvic bone is continuing to develop within the rotund belly.[9]

Juveniles have unicuspid scales, tricuspid scales, and pentacuspid scales.[9]

Triodon macropterus is harmless to humans unless eaten, at which point the species is considered poisonous.[2][4]

• Tetraodontidae
• Tetraodontiformes
• Ostraciidae
• Triacanthodidae