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Luidia sarsi: sea star magic
Here you are, minding your own business, and you come across a sea star (marine biologists will stab you in the hand with a fork for calling it a starfish). An orangy-white, five-armed rather unremarkable fellow, you might think. And you would be so, soooo wrong.
Luidia sarsi turns sexual reproduction upside down. You might think: mammy-sea star, daddy-sea star, eggs, seamen, larvae, new sea star. Nope. All is well until larvae: it swims around like any other zooplankton, minding its own business, all while a new sea star is forming inside the larvae. Eventually, the sea star “migrates” to the outside of the larvae, and they part ways. Sea star falls to the ocean floor and starts its sea starry life. But the larvae (if we can call it that now) continues to live as zooplankton.
So how to classify this?? In a way, there are two life forms here. Not two stages, but two life forms and three stages. So.. adult sea stars: seamen + eggs, and then a kind of larvae that kind of gives birth to the sea star. Then two life forms that go separate ways.
It blows my mind every time I think about it.