Krill are essential components of Antarctic ecosystems – they are important prey for fish, seals, penguins, and whales, and they influence carbon and nutrient cycling. This keystone role of krill means that in order to sustainably manage human impacts on Antarctic ecosystems, we need to understand the factors which influence krill populations.
One factor we don’t currently know much about is the role of parasites. Parasites are difficult to see within krill, and so until recently have been thought to be relatively rare in the Antarctic. Emerging genetic tools offer a more sensitive way to detect parasites, and early data suggests parasites may infect as many as one in ten krill, in certain times and places (Cleary et al. 2019).
When we look at parasites in other animals related to krill, we see that some parasites appear not to affect their host very much at all, some parasites make their host grow more slowly or have fewer offspring, and some parasites (called parasitoids) even kill their host.
In the ParaKrill project we generated new data on the types & distributions of parasites infecting krill, and on the impacts parasites have on the infected individuals. By combing these different types of data, we aimed to get a better understanding of what role krill-parasite interactions play in Antarctic ecosystems. We found a diverse assemblage of parasites within krill, including both single celled and multicellular parasites. We observed that female krill infested with parasites produced lower quality eggs, which may have implications for population dynamics. We also explored the impacts of parasites on krill growth and metabolism. Our results expand our understanding of the role of parasites, and have implications for sustainably managing the fishery for these small crustaceans in a changing environment.
