Nature never ceases to amaze in inventiveness:

> The tiny males never develop a shell, but instead develop a modified arm that he can detach onto a female's mantle to pass along his sperm. This arm can move on its own, wriggling toward the very center of the spiraling shell. This led certain researchers to mistake these lone male arms for "some form of a parasite or worm living inside the female," Villanueva said. A female argonaut can store a handful of these male arms until she is ready to spawn.