Welcome to the Marine Mili series, a regular column about all things marine! Durning this series I aim to inspire people to want to protect our oceans and all the marine life that call our oceans home. Hopefully after reading each column, you would have learnt something new including what we can do to help protect and preserve our oceans. You can follow me and my journey on my Instagram page: _marine_mili.
During spring these fortune cookies shaped sacs are a common sight on the beach. Have you ever wondered what these are? Most people think it is a type of jellyfish or jellyfish eggs/poo. These sacs are actually moon snail egg sacs that can hold thousands of eggs.
The mass of eggs will take in water and absorb it, then creating the crested shape we see at our local beaches.
Moon snails can range in size and grow up to about 13cm however some moon snail shells we see washed up on our beaches are only about five centimetres or under. These egg sacs can be between three to five times the size of the moon snail which the eggs came from.
The eggs that tend to be closer to the to the surface of the jelly capsule hatch first while eggs closer to the centre hatch afterwards as the oxygen supply is better. As all the eggs begin to hatch the jelly sac begins to break down.
Once all the eggs are hatched and out of the breaking down jelly sac, the eggs turn into snail larvae that is so tiny you would need a microscope to see them. They then float with the currents and grow rapidly to juveniles about a few centimetres long.
Have you ever wondered why there is a perfect hole in that seashell you just picked up at the beach?
Well, let me tell you, that is none other than a moon snail’s doing.
Moon snails aren’t the only creature who creates these holes in seashells, but they use their rough, drill-like tongue to put a hole in a live sea shell and suck out the creature inside.
Moon snails mainly eat bivalves which are two valves that fit together when closed like clams. If you do find a seashell with a hole in it, it isn’t guaranteed that hole is from a moon snail however it definitely could be.
Next time you are at the beach, if you see one of these fortune cookie shaped sacs, remember these are eggs ready to hatch. So please don’t step on them, throw them or squish them.