''Triodon macropterus'' (

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contra ...

the threetooth puffer and the black-spot keeled pufferfish) is a tetraodontiform fish, the only living species in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

''Triodon'' and family Triodontidae.Matsuura, K. (2014): Taxonomy and systematics of tetraodontiform fishes: a review focusing primarily on progress in the period from 1980 to 2014. ''Ichthyological Research, 62 (1): 72-113.''Gomon, M.F. & Bray, D.J. (2011): Threetooth Puffer, ''Triodon macropterus''
Fishes of Australia
Other members of the family are known from fossils stretching back to the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

. The threetooth puffer was first scientifically described by René Lesson in 1831 and is recognizable for its large belly flap which has the ability to blend into the body when fully retracted.

Etymology

The name ''Triodon macropterus'' comes from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

(, meaning 'three') and (or , , meaning 'tooth'), and refers to the three fused teeth that make up a beak-like structure.

Distribution and Ecology

The threetooth puffer is native to the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

, where it is found mainly around Australia and off the coast of Asia at depths from .Binohlan, C.B. & Reyes, R.B. ''Triodon macropterus'', Threetooth puffer i
FishBase
March 2021 version.Yamanoue, Y. et al. (19 July 2008). "A New Perspective on Phylogeny and Evolution of Tetraodontiform Fishes (Pisces: Acanthopterygii) Based on Whole Mitochondrial Genome Sequences: Basal Ecological Diversification?". ''BMC Evolutionary Biology''. 8 – via BioMedCentral. Its habitat is

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

, consisting of continental shelves,

slopes In mathematics, the slope or gradient of a line is a number that describes both the ''direction'' and the ''steepness'' of the line. Slope is often denoted by the letter ''m''; there is no clear answer to the question why the letter ''m'' is used ...

seamounts A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abr ...

, and knolls.Froese, R. & Pauly, D. (December 2019). "Triodon macropterus Lesson, 1831". ''WoRMS - World Register of Marine Science''. Retrieved March 12, 2021.

Diet and Digestion

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 Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

echinoids Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

, and

sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

.Johnson, G.D., and Britz, R. (29 January 2005). "A Description of the Smallest Triodon on Record (Teleostei: Tetraodontiformes: Triodontidae)." Ichthyological Research, vol. 52, no. 2, pp. 176–181. The intestinal tract of the threetooth puffer (the

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, and

intestines The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...

) is lined with several

papillae Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

, protrusions of the gut lumen. After the stomach, the tract branches off into a specialized sac-like compartment called Tyler's Pouch. Within the Tyler's Pouch the papillae are much larger in size and number compared to those prior. The role and function of Tyler's Pouch is largely unknown.

Adult Characteristics

The threetooth puffer reaches a maximum length of . 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. The flap is inflated by rotating the shaft-like pelvis downwards, exposing a black eye-spot contoured with yellow. This makes the animal appear much larger to predators, and less likely to be eaten. When danger is not present, the flap is retracted seamlessly into the body and the eye-spot is not visible. 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. 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. The threetooth puffer has ribs, a beak, and no pelvic fins which are all characteristics of

tetraodontiformes The Tetraodontiformes are an order of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the order Perciformes. The Tetraodontiformes are represented by 10 extant families and at least ...

. Adult scales have a rhombic base, and each has a median ridge from which several spines protrude. File:Triodon macropterus JNC2989 Fresh.JPG, Living specimen, belly flap half extended File:MHNT - Triodon bourse.jpg, Desiccated museum specimen File:Triodon.jpg, Illustrated specimen by

Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in nat ...

File:Triodon macropterus JNC2989 Eye.JPG, Eye File:Triodon macropterus JNC2989 Teeth.JPG, Beak-like structure composed of fused teeth File:Triodon macropterus JNC2989 Spot.JPG, Lateral eye-spot

Juvenile Characteristics

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. The head of the specimen makes up 45% of the length of its body, and its eyes make up 18% of its body length. As a juvenile, the pelvic bone is continuing to develop within the rotund belly. Juveniles have unicuspid scales, tricuspid scales, and pentacuspid scales.

Danger to Humans

''Triodon macropterus'' is harmless to humans unless eaten, at which point the species is considered poisonous.

References

Triodontidae Fish described in 1831 Monotypic fish genera Taxa named by René Lesson {{Tetraodontiformes-stub