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Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults. Amphibians breathe by means of a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat. [43]
Gosner stage is a generalized system of describing stages of embryonal and larval development in anurans (frogs and toads). The Gosner system includes 46 numbered stages, from fertilized embryo (stage 1) to the completion of metamorphosis (stage 46). It was introduced by Kenneth Gosner in 1960. [2]
Frogs may lay their eggs as clumps, surface films, strings, or individually. Around half of species deposit eggs in water, others lay eggs in vegetation, on the ground or in excavations. [136] [137] [138] The tiny yellow-striped pygmy eleuth (Eleutherodactylus limbatus) lays eggs singly, burying them in moist soil. [139]
About 25% of the species are oviparous (egg-laying); the eggs are laid in terrestrial nests rather than in water and are guarded by the female. For some species, the young caecilians are already metamorphosed when they hatch; others hatch as larvae. The larvae are not fully aquatic, but spend the daytime in the soil near the water. [15] [53]
A dragonfly in its final moult, undergoing metamorphosis, it begins transforming from its nymph form to an adult. Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. [1]
The eggs are laid in the spring, during heavy rains. Some larvae undergo metamorphosis while others are neotenic and retain their gills. In larger bodies of water where predatory fish like the bluegill (Lepomis macrochirus) are present, metamorphosis is more common. When ponds were dried it also showed higher rates of metamorphosis. [10]
A tadpole or polliwog (also spelled pollywog) is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found in adult amphibians, such as a lateral line, gills and swimming tails.
The young of some ovoviviparous amphibians, such as Limnonectes larvaepartus, are born as larvae, and undergo further metamorphosis outside the body of the mother. Members of genera Nectophrynoides and Eleutherodactylus bear froglets, not only the hatching, but all the most conspicuous metamorphosis , being completed inside the body of the ...