Influence of parasites on spawning success and egg quality in Antarctic krill Euphausia superba

Antarctic krill Euphausia superba are key components of Southern Ocean ecosystems and biogeochemical cycles, as well as the target of a growing commercial fishery. Understanding the drivers of variability in krill recruitment is key to managing this fishery sustainably. One potential driver which has received little attention is the role of parasites. We investigated the impact of natural parasite infestations in adult female krill on egg production and egg quality around South Georgia. DNA metabarcode sequencing was used to detect all eukaryotic parasites within krill bodies, while spawning success was determined through incubation experiments, and egg quality was assessed by quantifying key elements within each egg (carbon, nitrogen, hydrogen). E. superba in this area were infested with suctorian ciliates, eugregarine apicomplexans, and, less frequently, ellobiopsids. Parasite load was not associated with a reduced likelihood of producing eggs, but high parasite loads were associated with lower-quality eggs. This reduction in egg quality may reflect an energetic cost to parasite infestation, with implications for larval development and recruitment.