Pearl

cohesive bivalves

wiggly irritant injures

crusty self-defense

eloquent protective shield

oyster yields a starry pearl

I had 3 different conceptions while framing this tanka, the first being the direct inference of the biological formation of a pearl in an oyster, and the second about a motivational stimulus. The third perspective, not associated with the entire tanka, is a euphemism with a human hermaphrodite.