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Coloured scanning electron micrograph (SEM) of a female and male roundworm (Contracaecum rudolphii). The male has two needle-like mating structures, spicules, at the posterior end. C. rudolphii is the most important parasite of cormorants. The genus Contracaecum are parasitic nematodes belonging to the family Anisakidae. Fish are by far the main source of infection as they serve as intermediate host of the nematodes. The final hosts are marine mammals (e.g. seals) or piscivorous birds (e.g. cormorants and pelicans). Identification of these nematodes is important in terms of seafood safety and public health, as humans may be infected following consumption of infected seafood. Magnification: x10 when printed at 10cm wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/JANNICKE WIIK-NIELSEN/VETINST/SCIENCE PHOTO LIBRARY)