Red Kangaroo: Embryo Outside the Womb? Some day this little guy or girl will be about as tall as a man. But for now the weeks-old red kangaroo joey is roughly cherry-size, essentially an embryo outside the womb.
Shown about halfway through its 12-month gestation period in a computer-generated illustration, a lemon shark--like a human embryo--is literally connected to its mother via an umbilical cord attached to a placenta. But it wasn't always so.
Until about three months in the womb, baby sharks feed off a yolk sac. Once the embryo has depleted the yolk, the collapsed sac settles against the womb wall and shoots blood vessels into the wall, tapping into the mother's circulatory system.
By the time the embryo is six months old (pictured), it has a sense of smell 10,000 times sharper than a human's. This and other sensory adaptations--including electro-sensors that detect the faint voltage of other animals--will one day allow the shark to detect even a fin flick hundreds of feet away,
Parasitic Wasps: Alien on Earth
They may look peaceful in this gauzy digital simulation, but parasitic wasp embryos inspired the infamous "birth" scene in the 1979 horror flick Alien. Injected into a caterpillar by their mother, the once egg-encased wasp embryos develop for about 14 days. Then things get ugly.
In a biological attack unique in the animal world, the unassuming embryos use a virus in their DNA to paralyze their host. They bite their way out of the caterpillar and begin spinning cocoons.
As a final insult to the injured host, the caterpillar--apparently brain-addled by the virus--builds a silky blanket over its attackers and defends them against predators until the wasps emerge, fully formed, and take to the skies.
Emperor Penguin: Inside the Breathing Egg
Kicking back before getting down to the hard work of hatching--a several-day process--a late-stage emperor penguin embryo (shown in a digital illustration) breathes easy inside its egg, which is resting on the father penguin's feet while Mom is on a months-long fishing trip.
Unlike developing humans, a baby penguin can't tap into the oxygen in its mother's bloodstream. Instead, its umbilical cord is linked to blood vessels in a membrane attached to the egg's inner wall. Oxygen enters the embryo's blood via microscopic holes in the shell--turning the egg into a kind of surrogate lung.
After 64 days of development, the baby penguin will slowly smash its way out, and its mother, with any luck, will be waiting with fish.
