Physoclisti are, collectively, fishes that lack a connection between the
gas bladder and the
alimentary canal, with the bladder serving only as a
buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the ...
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
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