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Physoclisti
Physoclisti are, collectively, fishes that lack a connection between the gas bladder and the alimentary canal, with the bladder serving only as a buoyancy organ. Addition and removal of the gases from the gas bladder in such physoclistous fishes occurs through specialised structures called the gas gland and ovale respectively. The pneumatic duct that connects the gut and gas bladder is present in the embryos of these fish but it is lost during development. This anatomical state (the physoclistous condition) is believed to be evolutionarily derived from the ancestral physostomous state. Some fishes, such as eels, are anatomically physostomous, but their gas bladders function similar to those of physoclists. See also * Physostome Physostomes are fishes that have a pneumatic duct connecting the gas bladder to the alimentary canal. This allows the gas bladder to be filled or emptied via the mouth. This not only allows the fish to fill their bladder by gulping air, but al .. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Bladder
The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift via swimming, which expends more energy. Also, the dorsal position of the swim bladder means that the expansion of the bladder moves the center of mass downwards, allowing it to act as a stabilizing apparatus. Additionally, the swim bladder functions as a resonating chamber to produce or receive sound. The swim bladder is evolutionarily homologous to the lungs of tetrapods and lungfish, and some ray-finned fish such as bowfins have also evolved similar respiratory functions in their swim bladders. Charles Darwin remarked upon this in ''On the Origin of Species'', and reasoned that the lung in air-breathing vertebrates had derived from a more primitive swim bladder as a specialized form of enteral respiration. Some species, such as mostly bottom dw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swim Bladder
The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ (anatomy), organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift (force), lift via swimming, which expends more energy. Also, the Dorsum (biology), dorsal position of the swim bladder means that the expansion of the bladder moves the center of mass downwards, allowing it to act as a stabilizing apparatus. Additionally, the swim bladder functions as a resonating chamber (anatomy), resonating chamber to produce or receive sound. The swim bladder is evolutionarily homology (biology), homologous to the lungs of tetrapods and lungfish, and some ray-finned fish such as bowfins have also evolved similar respiratory functions in their swim bladders. Charles Darwin remarked upon this in ''On the Origin of Species'', and reasoned that the lung in air-breathing vertebrates had derived from a more primitive swim b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alimentary Canal
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 tract is the largest of the body's systems, after the cardiovascular system. The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines. Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled at the anus as feces. ''Gastrointestinal'' is an adjective meaning of or pertaining to the stomach and intestines. Most animals have a "through-gut" or complete digestive tract. Exceptions are more primitive ones: sponges have small pores ( ostia) throughout their body for digestion and a larger dorsal pore ( osculum) for excretion, comb jellies have both a ventral mouth and dorsal anal pores, while cnidarians and acoels have a single pore for both digestion and excretion. The huma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus, the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the Displacement (fluid), displaced fluid. For this reason, an object with average density greater than the surrounding fluid tends to sink because its weight is greater than the weight of the fluid it displaces. If the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physostome
Physostomes are fishes that have a pneumatic duct connecting the gas bladder to the alimentary canal. This allows the gas bladder to be filled or emptied via the mouth. This not only allows the fish to fill their bladder by gulping air, but also to rapidly ascend in the water without the bladder expanding to bursting point. In contrast, fish without any connection to their gas bladder are called physoclisti. The physostome fish encompass the bichirs, gars, a number of carps, trouts, herrings, catfish, eels and the lungfish. While the gas bladder in fish mainly serves as a buoyancy organ, some physostomes (though not all) can use their gas bladder as a lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ..., allowing them to live from atmospheric oxygen in conditions where aqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
