By Seaside Aquarium
Large jellyfish have been washing ashore causing a lot of people to ask why? The answer is simple yet complicated.
This simple answer is that this happens every year in the late summer and early fall. Jellyfish have two different body forms, medusa and polyp. Their medusa form is what you typically think of when imagining what a jellyfish looks like. Medusae reproduce through mass spawning, where eggs and sperm are released into the water. Fertilized eggs develop into free-swimming larvae called planulae. These flat, pear-shaped creatures eventually attach to a hard surface and develop into a polyp. Polyps resemble sea anemones and reproduce by splitting themselves in half producing a genetically identical polyp. They can do this numerous times creating a colony of polyps all with the same genetics. When ocean conditions are just right, the polyp starts a process called strobilation and they begin to bud off ephyra which develop into medusae. Polyps can live for years even decades but medusae tend to live for only a few short months (though in captivity some species can live up to a few years). When currents change or seas get rough, medusae wash ashore or get torn apart in the surf.
So don’t fret. Those lifeless jellies you see on the beach are essentially immortal as their genetics continue and clones of themselves will soon bud off their polyp form and roam the open ocean once again.
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Photos by Sam Heroux, Seaside Aquarium
