What You’re Looking At
A skate’s egg case—often called a “mermaid’s purse” (or “devil’s pocketbook”)—is a tough, protective capsule that forms around a single skate embryo before the mother deposits it on the ocean floor.
Key Features (Why It Looks Like That)
- Leathery, dark case: Built to protect the developing embryo in a harsh marine environment.
- Long, thin projections (“horns” or tendrils): These help the egg case catch on seaweed, eelgrass, or debris.
- Anchoring function: The projections act like natural ties so the case stays secured in place while the embryo develops.
Why Mermaid’s Purses Wash Up on Beaches
Empty egg cases are commonly found along shorelines because once the young skate hatches, the capsule may detach, drift, and wash ashore. Finding one can be a clue that egg-laying species live in nearby waters.
The Bigger Group: Elasmobranchs
Skates belong to a larger group called elasmobranchs, which includes:
- Sharks
- Skates
- Rays
How Sharks, Skates, and Rays Reproduce
Elasmobranchs use several reproductive strategies:
- Oviparous (Egg-laying):
- The animal lays eggs in protective cases.
- Common in skates and some sharks.
- Viviparous (Live birth):
- The baby develops inside the mother and is born live.
- Ovoviviparous (Aplacental viviparity):
- The mother produces eggs that hatch inside her body, and the young are then born live.
What the Photo Shows
In the image, the object being held is a dark, leathery mermaid’s purse with long trailing projections, matching the typical look of a skate egg case designed for anchoring on the seafloor.
Beachcombing Tip
If you find a mermaid’s purse, it may be:
- Empty (most common on beaches)
- Or potentially still developing if it appears fresh and intact
A simple rule is to avoid damaging any case you find and follow local guidance on handling marine life.
