continuous airbreathers, and most are obligatory οτι τα περισσοτερα βασιζονται στην αναπνοη ατμοσφαιρικου αερα και μονο
Air breathing fish can be divided into
obligate air breathers and
facultative air breathers. Obligate air breathers, such as the
African lungfish,
must breathe air periodically or they suffocate. Facultative air breathers, such as the catfish
Hypostomus plecostomus, only breathe air if they need to and will otherwise rely on their gills for oxygen. Most air breathing fish are facultative air breathers that avoid the energetic cost of rising to the surface and the fitness cost of exposure to surface predators.
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http://en.wikipedia.org/wiki/Fish