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How does direct development differ from the usual amphibian life cycle?
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birth
Sequential changes in the position of the child during labour.
The usual amphibian life cycle is biphasic, typically involving the deposition of eggs in water, which then hatch into free-living, aquatic larvae that must find their own food and escape predators. These larvae eventually undergo metamorphosisāa radical physiological and structural transformationāto adopt an adult body plan suitable for terrestrial or semiaquatic life.123
In contrast, direct development eliminates the free-swimming larval stage entirely. In this mode of development:45
- Developmental Environment: The entire process occurs within the egg capsule, often in terrestrial environments such as leaf litter, moss, or within specialized structures on the parent's body.45
- Hatching: Instead of emerging as larvae, the young hatch as miniature versions of the adult form.5
- Independence: Because the larval stage is bypassed, these individuals do not require an aquatic environment to complete their early development, effectively severing the species' reliance on water for reproduction.45
This evolutionary strategy is found across various amphibian groups, including many anurans, lungless salamanders, and some caecilians.5