engleski

Changes in the immune response during range expansion of the invasive signal crayfish Pacifastacus leniusculus

Investment in immunocompetence can have direct impacts on the invasion success. During range expansion, individuals enter the novel environment where they can benefit from both the increase or decrease in immune investment. Increased immune investment may be required during contact with novel pathogens, but it is also energetically costly for the dispersing individuals. Thus, if investment in immunocompetence drives range expansion, we would expect to observe differences in immune response along the invasion range of an invader. In this pilot study, we compared the immune response of one of the most successful crayfish invaders in Europe, the signal crayfish, along its invasive range in the Korana River, Croatia. Comparisons were made between individuals from the invasion core and invasion front sites, which were subjected to the same treatment in the laboratory. We measured the immune response parameters (total hemocyte count, encapsulation response, total and specific phenoloxidase and prophenoloxidase activity), morphological parameters and crayfish condition parameters (Fulton's condition factor, total plasma protein concentration). Immune response parameters were analysed separately, as well as their combined effect in order to measure the overall immune status. No significant differences were found in overall immune status between individuals from invasion core and invasion front. However, some parameters, i.e. the specific and total prophenoloxidase activity, exhibited significant differences – they were significantly higher in individuals on the invasion front compared to those in the invasion core, which potentially indicates higher immune investment in the individuals on the invasion front. We discuss our findings in the context of the theories regarding immune investment during the range expansion of the invasive species. This research was funded by Croatian Science Installation Grant (HRZZ UIP-2017-05-1720).

invasive species ; immunity ; hemolymph ; phenoloxidase ; prophenoloxidase

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