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Eggs in the sea…

Posted on: April 4, 2012

Port Jackson shark egg case

It’s Easter time! Whilst you’re consuming all that chocolate, take a moment to stop and think about what the eggs actually mean. We have eggs, chicks and rabbits at Easter to represent new life.

How does new life occur in the ocean though? Many will be familiar with annual coral spawning events that occur around the world. In Western Australia, at Ningaloo, the coral spawning event usually occurs after the full moon in March or April.

Many organisms in the ocean reproduce externally, meaning they release either sperm or eggs (or both in the case of hermaphrodites) into the water. Animals that reproduce in this way release large numbers of eggs and sperm to ensure that some survive.

Other animals, such as some sharks and rays, reproduce via internal fertilization and bear live young. These animals produce fewer offspring, however, have a greater chance of survival.

Use our Seacrets to Sex and Survival poster and Sex and the Sea article to find out more about how a range of marine animals reproduce, including sea stars, sea horses, sea slugs and deep-sea anglerfish! Investigate the methods these animals use to ensure survival of their species, and what challenges do they face? Which animals use external fertilization, and which use the internal method? Do sharks lay eggs, or give birth to live young?  How do you attract a mate if you are a crustacean, dhufish, or cuttlefish? Who gets the job of looking after the baby in the seahorse family?

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