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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 evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.
Whatever the reason, the drive led to internal fertilization and direct development (completing the tadpole stage within the egg). A striking parallel can be seen in the frog family Leptodactylidae, which has a very diverse reproductive system, including foam nests, non-feeding terrestrial tadpoles and direct development. The Diadectomorphans ...
Frogs have a two-stage life cycle, with the aquatic tadpole larva metamorphosing into the adult form. This tadpole was in the late stages of metamorphosis. Adults of this species are a similar ...
But, for as intriguing as frogs giving birth to live tadpoles may be, PLOS One says since researchers haven't witnessed their birth in the frog's natural environment, there's still the possibility ...
The tadpoles then swim out into the open water and rapidly complete their development. [121] Madagascan burrowing frogs are less fossorial and mostly bury themselves in leaf litter. One of these, the green burrowing frog ( Scaphiophryne marmorata ), has a flattened head with a short snout and well-developed metatarsal tubercles on its hind feet ...
The larvae of some organisms (for example, some newts) can become pubescent and do not develop further into the adult form. This is a type of neoteny. [5] It is a misunderstanding that the larval form always reflects the group's evolutionary history. This could be the case, but often the larval stage has evolved secondarily, as in insects.
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]