What Is a Mermaid's Purse?

Learn More About Marine Life

Developing embryo of Little Skate inside egg, Massachusetts, USA / Johnathan Bird / Photolibrary / Getty Images
Developing embryo of Little Skate, Raja erinacea, inside egg, Massachusetts, USA. Johnathan Bird/Photolibrary/Getty Images

Perhaps you've found a "mermaid's purse" on the beach. Mermaid's purses blend really well with seaweed, so you may also have walked right by one. Upon further investigation, you can learn more about what they are.

The enchantingly named structures are the egg cases of skates and some sharks. This is why they are also known as skate cases.

While some sharks bear live young, some sharks (and all skates) release their embryos in leathery egg cases that have horns and sometimes long tendrils at each corner. The tendrils allow them to anchor to seaweeds or other substrates. Each egg case contains one embryo. The case is made up of a material that is a combination of collagen and keratin, so a dried egg case feels similar to a fingernail. 

In some areas, such as in the Bering Sea, skates seem to lay these eggs in nursery areas. Depending on the species and sea conditions, the embryo may take weeks, months or even years to fully develop. When they hatch out of one end, the baby animals look like miniature versions of their skate or shark parents. 

If you find a mermaid's purse on the beach or are lucky enough to see a "live" one in the wild or in an aquarium, look closely -- if the developing skate or shark is still alive, you may be able to see it wiggling around. You also may be able to see it if you shine a light through one side. The egg cases on the beach are often light and already opened, which means the animal inside has already hatched and left the egg case. 

Where to Find a Mermaid's Purse

Mermaid's purses usually get washed or blown to the high tide line of the beach, and they often get wrapped up in (and blend in well with) seaweeds and shells. As you're walking along the beach, walk in the area where shells and ocean debris seems to have washed up, and you might be lucky enough to find a mermaid's purse. You may be more likely to find one after a storm. 

Mermaid's Purse Identification

Found a mermaid's purse on the beach and want to know where it is from? Skate and shark species vary by region, but there are some identification guides out there for you beachcombers wanting to identify your finds. Here are the ones I've found so far:

Conservation Factors

To learn about population sizes and reproduction, some organizations have launched citizen science efforts to have people report and send in egg cases they find on the beach. Click on the links below for more information on reporting mermaid's purses that you may find.

References and More Information

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Kennedy, Jennifer. "What Is a Mermaid's Purse?" ThoughtCo, Aug. 26, 2020, thoughtco.com/what-is-a-mermaids-purse-2291442. Kennedy, Jennifer. (2020, August 26). What Is a Mermaid's Purse? Retrieved from https://www.thoughtco.com/what-is-a-mermaids-purse-2291442 Kennedy, Jennifer. "What Is a Mermaid's Purse?" ThoughtCo. https://www.thoughtco.com/what-is-a-mermaids-purse-2291442 (accessed June 2, 2023).