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A fish's hypoxia tolerance can be represented in different ways. A commonly used representation is the critical O 2 tension (P crit), which is the lowest water O 2 tension (P O 2) at which a fish can maintain a stable O 2 consumption rate (M O 2). [2]
Whether fish sleep or not is an open question, to the point of having inspired the title of several popular science books. [ 2 ] [ 3 ] In birds and mammals, sleep is defined by eye closure and the presence of typical patterns of electrical activity in the brain, including the neocortex , but fish lack eyelids and a neocortex.
Breathing air is primarily of use to fish that inhabit shallow, seasonally variable waters where the water's oxygen concentration may seasonally decline. Fish dependent solely on dissolved oxygen, such as perch and cichlids , quickly suffocate, while air-breathers survive for much longer, in some cases in water that is little more than wet mud.
Another important adaptation that aids breathing while out of water is their enlarged gill chambers, where they retain a bubble of air. These chambers close tightly when the fish is above water, due to a ventromedial valve of the gill slit, keeping the gills moist, and allowing them to function while exposed to air.
Because of their capability to use atmospheric oxygen, these fish generally are not so dependent on a form of aeration in their tanks, as they can rise to the surface of the water and take a breath, or breathing apparatus. Many of the labyrinth fish are peaceful and do well in most community tanks. However, individual males, especially the ...
They are facultative air-breathers, accessing surface air to breathe when the water they inhabit is poorly oxygenated. [14] Their lungs are highly vascularized to facilitate gas exchange. Deoxygenated arterial blood is brought to the lungs by paired pulmonary arteries, which branch from the fourth efferent branchial arteries (artery from the ...
The original selective advantage offered by the jaw may not be related to feeding, but rather to increased respiration efficiency. [74] The jaws were used in the buccal pump still observable in modern fish and amphibians, that uses "breathing with the cheeks" to pump water across the gills of fish or air into the lungs in the case of amphibians ...
The climbing perch (Anabas testudineus) is a species of amphibious freshwater fish in the family Anabantidae (the climbing gouramis).A labyrinth fish native to Far Eastern Asia, the fish inhabits freshwater systems from Pakistan, India, Bangladesh and Sri Lanka in the west, to Southern China in the east, and to Southeast Asia west of the Wallace Line in the south.