Trahira

Trahira Hoplias malabaricus
White Piranha Serrasalmus rhombeus
Wimple Piranha Catoprion mento
Wolf Fish Hoplias malabaricus ...

Wolf fish, Tiger fish, Wolf tetra, Tiger tetra, Mud characin, Trahira, 'Piranha Eater'
This photo is courtesy of Esteban Falcato
from Buenos Aires, Argentina.
Close-up of adult ...

Loaches, trahiras, and many catfish breathe by passing air through the gut. Mudskippers breathe by absorbing oxygen across the skin (similar to what frogs do).

See also: Fish, Water, Characin, Piranha, Loach