physostome
Quick Summary
A physostome is a type of teleost fish that possesses a duct connecting its swim bladder to its alimentary canal. This duct allows for rapid gas exchange with the atmosphere. This contrasts with physoclists, which lack this duct.123
The swim bladder itself is a buoyancy organ found in most bony fish, helping them maintain depth. In physostomes, this connection enables them to regulate their buoyancy by expelling or taking in gas directly from their digestive tract. This feature is common in many relatively primitive teleosts. The superorder Ostariophysi, which includes a large percentage of freshwater fish species, are known as physostomes and have a refined sense of hydrostatic pressure.452
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