Editing Swamp eel (section)

==Description==

The [[marbled swamp eel]], ''Synbranchus marmoratus'', has been recorded at up to {{convert|150|cm|in|abbr=on}} in length,<ref name=EoF/> while the [[Monopterus indicus|Bombay swamp eel]], ''Monopterus indicus'', reaches no more than {{convert|8.5|cm|in|abbr=on}}.

Swamp eels are almost entirely finless; the [[pectoral fin|pectoral]] and [[pelvic fin]]s are absent, the [[dorsal fin|dorsal]] and [[anal fin]]s are vestigial, reduced to rayless ridges, and the [[caudal fin]] ranges from small to absent, depending on species.  Almost all of the species lack [[Scale (zoology)|scale]]s.  The eyes are small, and in some [[Cavefish|cave-dwelling]] species, they are beneath the skin, so  the fish is blind. The [[gill]] membranes are fused, and the gill opening is either a slit or pore underneath the throat. The [[swim bladder]] and ribs are also absent. These are all believed to be adaptations for burrowing into soft mud during periods of drought, and swamp eels are often found in the mud underneath a dried-up pond.<ref name=EoF>{{cite book |editor=Paxton, J.R. |editor2= Eschmeyer, W.N.|author= Liem, Karel F.|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|pages= 173–174|isbn= 0-12-547665-5}}</ref>

Most of the species can breathe air, allowing them to survive in low-oxygenated water, and to migrate overland between ponds on wet nights. The linings of the mouth and [[pharynx]] are highly vascularised, acting as primitive but efficient lungs. Although swamp eels are not themselves related to [[amphibian]]s, this lifestyle may well resemble those of the fish from which the land animals evolved during the [[Devonian]] period.<ref name=EoF/>

Although the adults are virtually finless, the larvae are born with greatly enlarged pectoral fins. The fins are used to propel streams of oxygenated water from the surface along the larva's body. The skin of the larva is thin and vascularised, allowing it to extract oxygen from this stream of water. As the fish grows, the adult air-breathing organ begins to develop, and it no longer requires the fins. At the age of about two weeks, the larva suddenly sheds the pectoral fins, and takes on the adult form.<ref name=EoF/>

Most species are [[protogynous]] hermaphrodites, that is, most individuals begin life as females, but later change into males. This typically occurs around four years of age, although a small number of individuals are born male and remain so throughout their lives.<ref name=EoF/>