A genus of parasitic roundworms in the family Anisakidae whose adults live in the stomachs of marine mammals such as whales and dolphins. Their larvae infect fish and squid as intermediate hosts — and accidentally humans, when Anisakis simplex larvae in raw or undercooked seafood attempt to colonise our gut, causing anisakiasis. The coiled, thread-like larvae are visible to trained inspectors who candle fillets over lights, but freezing at −20 °C for 24 hours or proper cooking reliably kills them. Rising global appetite for sushi and ceviche has made this once-obscure parasite a mainstream food safety concern.