There are many more types than the typical eggs we are used to for breakfast. I found a few to be interesting.
Shark eggs are strangely shaped eggs sometimes called a
mermaid’s purse. These consist of an egg case in a thin capsule made
of collagen. They often are square or rectangular with stringy or
pointy corner horns, but can come in a variety of odd shapes. Shark
eggs can wash up on the beach and are often hand-sized, although the
largest recorded was over six feet (2m) long. Female sharks lay
fertilized eggs onto the sea floor where they stay until they hatch,
not needing any more attention from their mother. Some shark eggs
contain several baby sharks which cannibalize each other before
hatching to ensure that only the strongest baby survives.
Octopus eggs are soft, translucent and often stuck on
overhangs of rock or coral. The females lay hundreds of thousands of
eggs at a time and will stay to guard them against hungry predators
until they hatch. This often takes so long that she begins to starve
and some octopuses will eat their own arms to survive. Once hatched,
they feed on microscopic organisms like plankton until they grow
large enough to live on the sea floor as adults.
Fish eggs are released as unfertilized eggs until and the
male injects them with sperm. In some species, the male and female
might never meet each other. Most have nothing more to do with the
eggs and leave them to develop on their own. Millions of soft eggs
are laid at once, so hungry predators will usually not destroy all
of them before they hatch. Some eggs are laid on secure surfaces
like rocks whereas others drift freely in the water, sometimes for
up to hundreds of kilometers.
We are familiar with bird and reptile eggs, which are
internally fertilized eggs and most are protected until they hatch.
Bird egg shells are made from calcium carbonate, which is also the
major component of sea shells and pearls. For camouflage, some egg
shells are colored or patterned with various other chemicals.
Dinosaur eggs sometimes contain fossilized baby dinosaurs
inside. Dinosaur eggs have many shapes, such as elongated spheres,
teardrops, and spherical. Some dinosaurs laid many eggs in a nest
and protected them while others laid eggs indiscriminately before
abandoning them. There are many types of dinosaur eggs, with the
largest being over 23 inches (60cm) long and 7.8 inches (20cm) wide.
Sponge, jelly, and coral eggs are similar way to most fish.
They do not have males and females. Instead, simple male and female
organs both occur on a single creature, which release eggs and sperm
into the water. Some reproduce asexually without male and female
organs, by simply releasing some of their cells to grow directly
into new individuals without needing to be fertilized.
Insect eggs are formed from stored sperm from a single
mating, which is also used for subsequent fertilization. Insects
will lay many eggs at once, and sometimes construct extravagant
nests or nurseries for them. Some eggs are laid in water and the
newborn insects spend the first portion of their life aquatically
before emerging into the air. Many insects will care for their eggs
after they are laid, with some ants and termites even controlling
the humidity and pH for them.
Amphibian eggs are often laid in water, surrounded by a gel
to keep them all together. When they hatch, the offspring are called
‘tadpoles’ and have gills, but no legs. They swim around like fish,
although initially they also lack a mouth and live directly off the
yolk left over from their egg by absorbing it through their skin.
Eventually, tadpoles grow mouths, legs, lungs, lose their tail, and
become fully adult. Some frogs carry their eggs to protect them or
if there is not enough water available.
Platypus eggs are an anomaly as platypuses are mammals. They
are warm-blooded, have hair, and produce milk. While the egg is
still inside a mother, she supplies it with nutrition from her own
body, similar to other mammals. Monotreme eggs are small, white, and
spherical. They are laid in small numbers and are fastidiously cared
for by their mother in her burrow until 4 to 6 months after
hatching. Platypuses do not have nipples to produce milk. They sweat
milk which their newly-hatched young drink.