It's the top view of part of the abdominal nerve cord of a white shrimp, Litopenaeus setiferus.
I have dissected out many nerve cords of many different species of crustaceans, and they are usually a slightly translucent white. So I was tickled by finding this unexpected leopard-like dotted pattern in this shrimp. I'd never seen anything like it before. I have no idea why it's coloured in this shrimp but not other species.