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The anamniotes are an informal group of craniates comprising all fish and amphibians, which lay their eggs in aquatic environments.They are distinguished from the amniotes (reptiles, birds and mammals), which can reproduce on dry land either by laying shelled eggs or by carrying fertilized eggs within the female.
After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst the amniote ancestors, the next major breakthrough appears to have involved a gradual replacement of the gelatinous coating covering the amphibian egg with a fibrous shell membrane. This allowed the egg to increase both ...
The temnospondyl Eryops had sturdy limbs to support its body on land Red-eyed tree frog (Agalychnis callidryas) with limbs and feet specialised for climbing Japanese giant salamander (Andrias japonicus), a primitive salamander The bright colours of the common reed frog (Hyperolius viridiflavus) are typical of a toxic species Wallace's flying frog (Rhacophorus nigropalmatus) can parachute to ...
The eggs of amphibians are typically laid in water and hatch into free-living larvae that complete their development in water and later transform into either aquatic or terrestrial adults. In many species of frog and in most lungless salamanders (Plethodontidae), direct development takes place, the larvae growing within the eggs and emerging as ...
[62] [63] The amniote egg would necessarily have had to evolve from one with an anamniote structure, as those found in fish and modern amphibians. [59] In order for such an egg to excrete CO 2 on land without the specialized membranes to aid in respiration, it would have to be very small, 1 cm in diameter or smaller. Such very small eggs with ...
The eggs of fish and amphibians are jellylike. Cartilagenous fish (sharks, skates, rays, chimaeras) eggs are fertilized internally and exhibit a wide variety of both internal and external embryonic development. Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them.
The spawn (eggs) of a clownfish.The black spots are the developing eyes. Spawn is the eggs and sperm released or deposited into water by aquatic animals.As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is known as spawning.
Life in Cold Blood is a BBC nature documentary series written and presented by David Attenborough, first broadcast in the United Kingdom from 4 February 2008 on BBC One. [1]A study of the evolution and habits of amphibians and reptiles, it is the sixth and last of Attenborough's specialised surveys following his major trilogy that began with Life on Earth, hence a ninth part for the eight ...