DIET AND TROPHIC NICHE OF THE INVASIVE SIGNAL CRAYFISH IN THE FIRST INVADED ITALIAN STREAM ECOSYSTEM

We evaluated the seasonality of diet and trophic niche of invasive signal crayfish (Pacifastacus leniusculus) in order to estimate the ecological role and effects on native communities of the first Italian stream ecosystem invaded by this species. We studied the differences in food source use between sexes, life stages and seasons using carbon and nitrogen stable isotope analysis. Results indicated that signal crayfish adults and juveniles diets mainly rely on macroinvertebrates and periphyton using mostly same food sources and occupying an equivalent trophic niche. However, males diet seems to differ between adults and juveniles, indicating diet shift during their life stages. Moreover, any significant differences were found in adults and juveniles diets between summer and autumn seasons. Our findings suggest that signal crayfish juveniles and adults exhibited similar feeding habits regardless of seasonality and that both are likely to pose negative effects on macroinvertebrate communities of this Italian stream ecosystem