Editing Bladder (section)

=== Fish ===
The gills of most [[teleost]] fish help to eliminate ammonia from the body, and fish live surrounded by water, but most still have a distinct bladder for storing waste fluid. The urinary bladder of [[teleost]]s is permeable to water, though this is less true for freshwater dwelling species than saltwater species.<ref name="Bentley2013">{{cite book|url=https://books.google.com/books?id=U0D3BwAAQBAJ&pg=PA143|title=Endocrines and Osmoregulation: A Comparative Account in Vertebrates|date=14 March 2013|publisher=Springer Science & Business Media|isbn=978-3-662-05014-9|author=P.J. Bentley}}</ref>{{rp|p. 219}} In freshwater fish the bladder is a key site of absorption for many major ions<ref name=":2">{{Cite journal |last1=Takvam |first1=Marius |last2=Wood |first2=Chris M. |last3=Kryvi |first3=H. |last4=Nilsen |first4=Tom O. |date=2023-06-29 |title=Role of the kidneys in acid-base regulation and ammonia excretion in freshwater and seawater fish: implications for nephrocalcinosis |journal=Frontiers in Physiology |volume=14 |doi=10.3389/fphys.2023.1226068 |doi-access=free |issn=1664-042X |pmc=10339814 |pmid=37457024}}</ref> in marine fish urine is held in the bladder for extended periods to maximise water absorption.<ref name=":2" /> The urinary bladders of fish and [[tetrapod]]s are thought to be analogous while the former's swim-bladders and latter's [[lung]]s are considered homologous.

Most fish also have an organ called a [[swim-bladder]] which is unrelated to the urinary bladder except in its membranous nature. The [[loach]]es, [[pilchard]]s, and [[herring]]s are among the few types of fish in which a urinary bladder is poorly developed. It is largest in those fish which lack an air bladder, and is situated in front of the [[oviduct]]s and behind the [[rectum]].<ref>{{Cite book|title=Lectures on the comparative anatomy and physiology of the invertebrate animals|last=Owen|first=Richard|publisher=Longman, Brown, Green, and Longmans|year=1843|location=London|pages=283–284|url=https://books.google.com/books?id=pNpPpKj4_tgC}}</ref>