More on Sharks

Mermaid’s purses (eggcases)

As we’re learning oh so well, Chondrichthyes are quite the unique class of fish. These sharks, skates and rays are equipped with skeletons made of boneless, flexible cartilage, true upper AND lower jaws, electric-field sensory organs (Ampullae of Lorenini).. the list goes on. The males even have clingy claspers under their bellies (more on those later). But one popular trait specific to some elasmobranch species is the rigid eggcase, colloquially the mermaid’s purse or devil’s purse. Check out the photos for more details about these strange shark makers!

Eggcases aren’t like anything else in the sea. They are leathery, rounded-rectangular-ish, dark colored and stiff — All traits to better hide them along the seabed from predators! Think of them as birds eggs: they are fertilized before they are laid; their shells are protein-based and collagen-like and also have hooks to better latch onto substrate or natural stone seafloor so they don’t get carried far away from where their mothers dropped them off.

Some live-bearing sharks may keep eggcases inside themselves rather than laying them on the sea floor, but these eggs aren’t always rigid like mermaids purses. Rather, they can be soft and squishy like water balloons! The embryo sharks absorb these yolk sacs until they are ready to be born ready-to-swim into the ocean blue.


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