wiggly irritant injures
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.
When a foreign particle, say sand, enters the region between an oyster’s mantle and shell that is present in two parts (bivalves), the oyster’s natural reaction is to cover up that irritant to protect itself. This protection is layered with a secretion called nacre that lines the inside of its shell and eventually forms a lustrous pearl.
The second one was a motivational stimulus that emphasizes the need to handle pain. The treasures (pearl) of the world are formed only after the oyster (human) experiences injuries and becomes strong from within (self-defense) to heal itself and face any hardships thereon with its own protective shield.
Considering the third viewpoint, pearls are perceived as hermaphrodite people who are born possessing both male and female (denoted as bivalves) reproductive organs (often not developed fully). These people are not transgenders. It is a rare type of intersex caused by the merging of a male and female embryo during pregnancy. Likewise, the formation of a natural (or oriental) pearl is a rare occurrence too. Also, the pearl oysters are protandrous hermaphrodites showing successive sex reversal during their existence as a reaction to various factors that influence them.