Parental care: A step further
A West African frog Nectophrynoides has taken parental effort even further. These frogs have internal fertilization with the fertilized eggs retained in the oviduct. Tadpoles develop, complete with mouths and external gills and they feed within the oviduct on tiny white flakes excreted from its walls. After nine months development which is co-ordinated with the arrival of the first rains, the female gives birth, by bracing her body against the ground with her forelegs and then inflating her lungs to full capacity which in turn swells the abdomen and squeezes the young out by pneumatic pressure.
The tiny frog Rhinoderma found in southern Chile deposits her eggs on moist ground, the males sit in groups around the eggs and guards them. When developing eggs move within the gelatinous coats, the males take the eggs into their large vocal sacs where they continue developing until they are fully-formed froglets. Phyllobates subpunctatus, one of the South Americanpoison dart frogs (Family Dendrobatidae), also lays the eggs on moist ground in close proximity to a guarding male frog. When the tadpoles hatch they wriggle themselves onto the male's back, where his copious quantities of mucous keeps them attached and prevents them from drying out. These tadpoles have no gills, but obtain oxygen by absorbing it through the skin of their body and from the surface areas of their greatly enlarged tails.