Dietary similarities between native swimming crab Achelous spinimanus (Latreille, 1819) and invasive Charybdis (Charybdis) hellerii (A. Milne-Edwards, 1867) in Santa Catarina, South Brazil

Abstract

Achelous spinimanus (Latreille, 1819) constitutes an ecologically and commercially important species along the South America coast. Over the last three decades, this native species has been exposed to the introduction of Charybdis (Charybdis) hellerii (A. Milne-Edwards, 1867), a potential competitor for the same substrate. Invasive species often show significant dietary adaptability which can impact native species and coastal ecosystems. This study compares the diet composition of C. (C.) hellerii and the native A. spinimanus. The stomachs of 66 A. spinimanus and 180 C. (C.) hellerii were analyzed, and the Alimentary Importance Index (IAi) was calculated. Trophic comparison was assessed using the Pianka index. Crustacean represented the most important food item, followed by mollusks for both species, which exhibited high similarity, suggesting a possible competition for resources. Results reveal dietary overlap and highlight the generalist feeding strategy of the invasive species during its establishment phase. These patterns suggest potential long-term ecological impacts on native crab populations. Overall, the study offers a baseline for future assessments on trophic interactions and the consequences of biological invasions in coastal environments.