Ecology of marine mammal parasites

Marine mammals exhibit unique adaptations for life in aquatic environments worldwide. They play crucial roles in ecosystem dynamics but face threats from human activities, leading to population declines and endangerment. Despite their significance, marine mammal parasites are often overlooked in research, though they play vital roles in host health and ecosystem function. Both protists and metazoan parasites can impact host populations, leading to decreased fitness and mortality of marine mammals. However, research on marine mammal parasites is hindered by limited opportunities for sampling free-ranging and vulnerable wildlife. While traditional morphological analyses and long-term datasets aid parasite study, molecular methods are increasingly utilised. Understanding marine mammal parasites is crucial from a One Health perspective, not only for ecosystem health but also for public health, given the potential for zoonotic disease, yet knowledge gaps persist, particularly in certain geographic areas and for certain marine mammal host and parasite species. The changing marine environment can accelerate parasitism dynamics, necessitating ongoing research. This chapter reviews marine mammal parasite diversity, life cycles and pathogenicity and highlights ecological differences between hemispheres, underscoring the importance of continued investigation in this field.