Editing Frog (section)

====Tadpoles====
[[File:Frog spawn time-lapse.gif|thumb|Frogspawn development]]

The larvae that emerge from the eggs are known as tadpoles (or occasionally polliwogs). Tadpoles lack eyelids and limbs, and have cartilaginous skeletons, gills for respiration (external gills at first, internal gills later), and tails they use for swimming.<ref name="Duellman">{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/29023/Anura/40603/From-tadpole-to-adult |title=Anura: From tadpole to adult |author1=Duellman, W. E. |author2=Zug, G. R. |encyclopedia=Encyclopædia Britannica |access-date=July 13, 2012}}</ref> As a general rule, free-living larvae are fully aquatic, but at least one species (''[[Nannophrys ceylonensis]]'') has semiterrestrial tadpoles which live among wet rocks.<ref>{{cite journal |author1=Wickramasinghe, Deepthi D. |author2=Oseen, Kerri L. |author3=Wassersug, Richard J. |year=2007 |title=Ontogenetic Changes in Diet and Intestinal Morphology in Semi-Terrestrial Tadpoles of ''Nannophrys ceylonensis'' (Dicroglossidae) |journal=Copeia |volume=2007 |issue=4 |pages=1012–1018 |jstor=25140719 |doi=10.1643/0045-8511(2007)7[1012:ocidai]2.0.co;2|s2cid=86244218 }}</ref><ref>{{cite web|url=http://amphibiaweb.org/cgi-bin/amphib_query?where-genus=Nannophrys&where-species=ceylonensis |title=''Nannophrys ceylonensis'' |author=Janzen, Peter |date=May 10, 2005 |work=AmphibiaWeb |publisher=University of California, Berkeley |access-date=July 20, 2012}}</ref>

From early in its development, a gill pouch covers the tadpole's gills and front legs. The lungs soon start to develop and are used as an accessory breathing organ. Some species go through metamorphosis while still inside the egg and hatch directly into small frogs. Tadpoles lack true teeth, but the jaws in most species have two elongated, parallel rows of small, [[keratin]]ized structures called keradonts in their upper jaws. Their lower jaws usually have three rows of keradonts surrounded by a horny beak, but the number of rows can vary and the exact arrangements of mouth parts provide a means for species identification.<ref name=Stebbins2/> In the Pipidae, with the exception of ''[[Hymenochirus]]'', the tadpoles have paired anterior barbels, which make them resemble small [[catfish]].<ref name=Pipidae/> Their tails are stiffened by a [[notochord]], but does not contain any bony or cartilaginous elements except for a few vertebrae at the base which forms the urostyle during metamorphosis. This has been suggested as an adaptation to their lifestyles; because the transformation into frogs happens very fast, the tail is made of soft tissue only, as bone and cartilage take a much longer time to be broken down and absorbed. The tail fin and tip is fragile and will easily tear, which is seen as an adaptation to escape from predators which try to grasp them by the tail.<ref>{{cite journal|last1=Hoff|first1=K. vS.|last2=Wassersug|first2=R. J.|title=Tadpole Locomotion: Axial Movement and Tail Functions in a Largely Vertebraeless Vertebrate|journal=Integrative and Comparative Biology|date=February 1, 2000|volume=40|issue=1|pages=62–76|doi=10.1093/icb/40.1.62|doi-access=free}}</ref>

Tadpoles are typically [[herbivore|herbivorous]], feeding mostly on [[alga]]e, including [[diatom]]s filtered from the water through the [[gill]]s. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles, and fish. The Cuban tree frog (''Osteopilus septentrionalis'') is one of a number of species in which the tadpoles can be [[Cannibalism|cannibalistic]]. Tadpoles that develop legs early may be eaten by the others, so late developers may have better long-term survival prospects.<ref>{{cite journal |author=Crump, Martha L. |year=1986 |title=Cannibalism by younger tadpoles: another hazard of metamorphosis |journal=Copeia |volume=1986 |issue=4 |pages=1007–1009 |jstor=1445301 |doi=10.2307/1445301}}</ref>

Tadpoles are highly vulnerable to being eaten by fish, [[newt]]s, predatory [[diving beetle]]s, and birds, particularly [[water bird]]s, such as [[stork]]s and [[heron]]s and [[domestic duck]]s. Some tadpoles, including those of the [[cane toad]] (''Rhinella marina''), are poisonous. The tadpole stage may be as short as a week in explosive breeders or it may last through one or more winters followed by metamorphosis in the spring.<ref>{{cite book |title=A Natural History of Amphibians |last=Stebbins |first=Robert C. |author-link1=Robert C. Stebbins|author2=Cohen, Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |pages=173–175 }}</ref>