D) Discuss the functional role of the swim bladder in Actinopterygi. Include a d
ID: 3164599 • Letter: D
Question
D) Discuss the functional role of the swim bladder in Actinopterygi. Include a detailed explanation for how 'gas' within the swim bladder is adjusted as a fish descends and then as it ascends the water column. Be sure to explain where the 'gas' is sourced from within the body and how it is removed. Include in your answer the following terms: gas gland, neutral buoyancy, ovale, rete mirabile, and constrictor muscles. Finally, briefly describe the analogous organ used by Chondricthyes to achieve buoyancy and how this differs from the swim bladder.Explanation / Answer
Swim bladder is a gas-filled sac or pouch present in the body of bony fishes, which helps it to maintain and control neutral buoyancy at various depths of water column.,as a result the fish neither drowns nor floats.
Actinopterygii are ray-finned fishes, they are the class of the bony fishes in which lungs is transformed into swimbladder, it is a white shiny saccular organ developed as a diverticulum from the wall of pharynx in gut, it helps in buoyancy. Fish with swim bladders can control the amount of gas in the bladder and it helps in controlling their buoyancy. This characteristic helps them in ascending and descending in water ,which the fins used to do, due to development of swim bladder fins are no longer required .
Swim bladder usually consists of two gas-filled sacs present in the dorsal portion of the fish in some only a single sac present. It's walls are flexible they contract or expand based on the surrounding pressure.Walls of the swim bladder contains very few blood vessels lined with guanine crystals, this keeps the gland impermeable to gases. By adjusting the gas pressurising organ using the gas gland or oval window the fish gets neutral buoyancy and ascend or descend . Due to its dorsal position, it gives the fish lateral stability.
In physostomous swim bladders (where air bladder is connected to digestive tract by an open duct), called pneumatic duct, it allowes the fish to fill up the swim bladder by "gulping" air. Excess gas is removed in a similarly.
In physoclistous fishes where the connection to the digestive tract is lost, in early stage ,these fish rise to the surface to fill their swim bladders, in later stage, the pneumatic duct disappears, and the gas(usually oxygen) comes by gas gland to the bladder to increase its volume as a result buoyancy increases. To bring gas to the bladder, the gas gland excretes lactic acid and produces carbon dioxide. as a result the acidity causes the hemoglobin of the blood to lose its oxygen , and this diffuses partly into the swim bladder. The blood flowing back to the body first enters a rete mirabile where the excess carbon dioxide and oxygen produced in the gas gland diffuses back to the arteries supplying the gas gland. As a result a very high gas pressure of oxygen is obtained in swim bladder, which helps in fishes like eels to maintain neutral buoyancy as they stay in deep water and require more pressure .
swim-bladder helps the fishes to swim at any depth with the least effort. When a fish likes to sink, the specific gravity of the body is increased, and when it ascends the swim-bladder is expanded and the specific gravity is decreases. By such adjustment, a fish can maintain equilibrium at any level.Gas is sourced from the circulatory system .
The analogous organ in chondrichthyes to achieve buoyancy is oil filled liver. In Chondrichthyes ( or cartilaginous fish) oil filled liver control their buoyancy. The oil lightens the shark’s heavy body and prevents it from sinking and also saves the sharks energy. Oily liver contains the oil squalene,which helps it to remain neutrally buoyant.
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