First record of a Kabatana sp. microsporidium infecting fish in the Atlantic Ocean

Two-spotted goby Gobiusculus flavescens from the Swedish Gullmarsfjord regularly present subcutaneous creamy-white patches in the body musculature, associated with Kabatana sp. infection. Analysis of the 16S rRNA gene of the microsporidium showed 98.54% homology with Kabatana newberryi infecting a marine goby from California, indicating that the Swedish microsporidium is either a different strain of K. newberryi or a closely related species. This represents the first record of a Kabatana species in the Atlantic Ocean. The genetic similarity of the 2 microsporidia was paralleled by close infection phenotypes. Infected muscle fibres were swollen compared to adjacent non-infected fibres, and mature spore masses were found throughout the skeletal musculature. No xenoma formation was detected. Since G. flavescens is an established model species in behavioural ecology, the host-parasite system is ideally suited for testing how microsporidian infections affect host behaviour and fitness.