Mermaid purses are distinctive objects found along coastlines, often mistaken for seaweed or other debris. They are a significant part of marine life, offering a unique glimpse into the reproductive strategies of certain ocean dwellers.
Understanding Mermaid Purses
A mermaid purse is a protective casing for the developing embryo of specific marine animals. These tough, leathery pouches safeguard young creatures during their early developmental stages. They vary in appearance, commonly black, brown, or dark green, and can feel somewhat like dried leaves or plastic.
They range in shape and size, from rectangular or pillow-shaped with distinct horns to more rounded forms with long, curly tendrils. Composed primarily of keratin, the same protein found in human hair and fingernails, the casing provides durability and flexibility. This design protects the embryo from predators and harsh ocean conditions.
Who Lays Mermaid Purses
Mermaid purses are produced by oviparous cartilaginous fish, meaning those that lay eggs rather than giving birth to live young. Skates lay cases that are typically rectangular with horns at each corner to anchor them to the seafloor. Certain shark species, such as catsharks, horn sharks, and bullhead sharks, also produce them. Catshark egg cases often have long, string-like tendrils that can entangle with seaweed to secure them.
Chimaeras, ancient relatives of sharks and rays, also lay distinctive, often spindle-shaped or bottle-shaped cases with wide ridges. While many shark species give birth to live young, a significant number of cartilaginous fish, including sharks, skates, and chimaeras, reproduce by laying these protective cases. The specific design of the mermaid purse often provides clues about the species that laid it.
Where to Find Them
Mermaid purses are often found washed ashore on beaches, especially along the high tide line, tangled among seaweed and marine debris. Stormy weather and strong currents can dislodge these cases from their underwater anchor points. They may also settle in rock pools or be blown by wind further back into sand dunes.
Live egg cases are laid on the seafloor, often in sandy or rocky areas or attached to seaweed in kelp forests. However, cases found on beaches are typically empty, as the young marine animal has usually hatched and departed. Divers and snorkelers might occasionally spot live, attached egg cases underwater, but these should not be disturbed.
What to Do If You Find One
If you find a mermaid purse, determine if it is empty or contains a developing embryo. Holding the case up to a light source can reveal if a marine creature is inside, as some cases are translucent. Live embryos require oxygenated seawater to survive, and removing them from their environment can be harmful.
If a live embryo is present, gently return the egg case to the ocean. Ideally, place it in a calm area below the low tide line, perhaps anchoring it to seaweed or a rock, to give the embryo the best chance of survival. If empty, it is harmless to keep as a souvenir. You can also contribute to marine science by reporting your findings to citizen science initiatives, such as the Shark Trust’s Great Eggcase Hunt, to help track species distribution and nursery areas.