Infected half-eaten lagoon sand shrimp (Gammarus insensibilis). This detached head from a half-eaten lagoon sand shrimp is infested with parasitic worms. This amphipod crustacean, which reaches lengths of 20 millimetres, is found in coastal lagoons. The life cycle of the parasitic trematode (flatworm) Microphallus papillorobustus includes this shrimp as an intermediate host. When infected, the shrimp swims upwards, making it more vulnerable to predation by seagulls and other seabirds. The flatworm's eggs are transmitted in the faeces of the seabirds, completing the life cycle.