Tetraodontiformes are an order in the superclass of bony fish with approximately 430 species.
When diving in the Canary Islands, we find representatives of the families of Triggerfishes, Filefishes, Pufferfishes, Porcupinefishes and Ocean Sunfishes, although the latter requires a lot of luck.
Tetraodontiformes species have almost exclusively a squat, tall, diamond-shaped, round or angular and rigid body.
Furthermore back and anal fin, are symmetrically opposite, and form the main swimming organ in most Tetraodontiformes. The tail fin is only intended to change the direction. An exception are the Ocean Sunfishes. In them, the tail fin is only present in the larval stage and is replaced by a seam after complete metamorphosis.
In principle, the anal fin has no spinal rays.
Porcupinefishes move mainly through wavy movements of the wide pectoral fins.
A further feature that all Tetraodontiformes share are the small, round or slit-shaped gill openings, which can be found directly at the beginning of the pectoral fin. In addition, the narrowing of the gill opening results from the fusion of the gill membrane with the trunk skin.
Tetraodontiformes have a small mouth compared to the body, which is occupied with few teeth. Usually they are fused into tooth plates.
There are differences in the scales. Thus, Triggerfishes have normal scales, Pufferfishes do not have scales, in case of Cofferfishes they are converted into large plates and in Porcupinefishes and many Pufferfishes they are converted into erectable spines.
Tetraodontiformes have the smallest number of vertebrae among all fishes. It is a maximum of 30, but usually less than 20. Cofferfishes of the genus Ostracion have, for example, only 14 vertebrae.
As already mentioned above, some of the families lack the pelvic bones. These were reduced, together with the pelvic fins. Many species are also missing the ribs.
All kinds of fishes, except the Ocean Sunfishes, have a swim bladder. Therefore, the skeleton of the Ocean Sunfishes is only slightly ossified in order to save weight in this way.
Tetraodontiformes have merged jaw bones and the parietal, nasal, extrascapular, intercalar and infraorbital are absent. In addition, the lateral line is no longer present on the head.
The Mola mola is the largest representative of the Tetraodontiformes and the heaviest bony fish with a maximum of 2.3 tons.
While the tail fins are the driving force of most fish, the Tetraodontiformes are usually the pelvic finsor the back and anal fin.
Some species can make sounds by crunching their teeth or a vibrating the swim bladder.
There are, after all, twelve species which are pure fresh water species.