The characteristic of a parasitic thing is that it feeds off the host without adding any benefit to it.
That is not characteristic of the fertilization of the human egg by sperm. They literal add to each other to make something new.
Believe it or not, lobster and crabs are crustaceans and are a part of the arthropod family, which include caterpillars, cockroaches, and spiders!
A Galactic Funking Hunt Wit Not Wont