02 Apr Did you know? Corals are born in a colorful underwater “blizzard”

Hard (or stony) corals reproduce by releasing their eggs and sperm all at the same time. Some corals are hermaphroditic releasing packages that contain both eggs and sperm. Somehow it works out that dozens of species release eggs and sperm at just the right time at particular times of the year.

The phenomenon brings to mind an underwater blizzard with billions of colorful flakes cascading in white, yellow, red, and orange. This synchronicity is crucial, because the “blizzard” makes it more likely that fertilization will occur.

But how does a tube sperm sponge know not to mate with a coral egg? Somehow nature works it out. In this primordial soup of life, eggs and sperm of each similar species float to the surface and find each other.

It’s in this magical moment of fertilization that larvae are created. Some of the larva free float as far as 160 kilometers and then settle to the bottom where they find a patch of seafloor to call home. Here they morph into their adult form called a polyp.

Hundreds of generations of polyps each build tiny cup shaped homes by secreting a hard skeleton of limestone. After the polyps die, others land on top and form new skeletons. Gradually a huge coral reef is built beneath them. The abandoned homes, billions upon billions of them are what form these huge coral reefs – one of the largest living creatures in the world.

Watch this video to find out more: https://video.nationalgeographic.com/video/coralreef_spawning

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Coral Triangle Center