About this time of year, the beaches of southwest Florida are invaded by creepy-looking, snake-like things washed up in the wrack line.
These are the egg cases of the lightning whelk (Busycon contrarium). The long coiled structure – sometimes known as a mermaid’s necklace – is made of up to 200 individual egg pouches linked to one another.
This entire egg chain is attached to the bottom of the ocean at the smallest end of the egg-case cluster. During periods of heavy storm action, they are dislodged and washed ashore. The developing embryos die once the egg cases are heated and dried out in the sun.
Each pouch contains about 30 fertilized eggs and some egg-case clusters can have between 150 and 200 pouches – making for a total number of offspring in the neighborhood of 4000 to 6000!
Early in the spring, the stranded egg cases have embryos in the early stages of development – cut one open and it looks like the inside of a chicken egg, but with 30 tiny yolks, rather than one large one. Later in the spring, the embryos have developed the earliest stages of their shell, the protoconch. This is the shell these lightning whelks will live in and grow for the rest of their lives.
So if you find a dried creepy, snake-like thing in wrack line, pick it up and have a look. Then give it a shake, you might find it to be full of the smallest shells you will ever find on the beach – lightning whelk protoconchs.