Sinistral and dextral

Okay kiddo, there are some creatures in the world called gastropods (say gas-tro-pods) which are sea snails that have shells on their backs. Some of these sea snails will twist their shells either to the left or to the right as they grow. If the shell twists to the left, we say it is sinistral (say sin-is-tral) and if it twists to the right, we say it is dextral (say dex-tral).

It’s kind of like when you tie your shoelaces, you either tie them with the bow to the left or to the right. That’s like the shell of the sea snail, it grows in either a left or right direction. The snails that grow in one direction or the other may eat different things, move in different ways or find mates in different ways. It’s like some people are left handed and some are right handed, they do things in their own way which is comfortable for them. Some species of gastropods will always have sinistral shells and some will always have dextral shells, it just depends on what species they are.