Physoclisti are, collectively, fishes that lack a connection between the
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, ...
and the
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. ...
, with the bladder serving only as a
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 t ...
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 ...
References
Fish Physiology Volume 4, 1970, Pages 413-443 The Nervous System, Circulation, and Respiration: The Swim Bladder as a Hydrostatic Organ, Johan B. Steen
External links
{{diversity of fish
Fish anatomy