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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 behavior of an amphibian hatchling, commonly referred to as a tadpole, is controlled by a few thousand neurons. [4] 99% of a Xenopus hatchling's first day after hatching is spent hanging from a thread of mucus secreted from near its mouth will eventually form; if it becomes detached from this thread, it will swim back and become reattached, usually within ten seconds. [4]
"Fewer than a dozen of the 6455 species of frogs in the world are known to have internal fertilization, and of these, all but the new species either deposit fertilized eggs or give birth to froglets."
The coverings over the eggs will remain in the wild until the brood emerges. [15] The embryos develop through to the tadpole stage inside these pockets but do not emerge as tadpoles, instead remaining in their chambers until complete development to toadlet stage. The young toads grow a tail during their growth, but these will only be temporary ...
After they hatch, the tadpoles fall into the waters below. [15] The tadpoles are elongated, with powerful tails and low fins, suited for fast-flowing water. [11] Outside of the breeding season, some species live in the canopy. The majority of amphibians use cutaneous respiration, or the process of breathing through the skin.
Since the 1990s, the series has been divided into two levels. Stage 1 books "explain simple and easily observable science concepts for preschool- and kindergarten-age children." Subjects covered in Stage 1 titles include the human body, plants, animals and "the world around us."
Darwin's frog is a small species with a snout–to–vent length of 2.2 to 3.1 cm (0.9 to 1.2 in). The snout is elongated into a fleshy proboscis which gives the head a triangular shape. The limbs are relatively long and slender. The front feet are not webbed, but some of the toes on the back feet usually are. [4]
If they do resort to cannibalism, their bodies can transform. They "develop larger heads, sharp beaks, stronger jaw muscles, and shortened intestine". [9] Researchers have concluded that this is an adaptive trait because it accelerates the rate of growth of the tadpoles by allowing for an increased caloric intake. [9]