Paradise under threat: the successful invasion of the freshwater shrimp Neocaridina davidi and its parasites on La Reunion Island

Abstract

Invasive species are one of the major threats to global biodiversity, particularly in hotspots of endemic species, such as oceanic insular ecosystems. Tropical and subtropical islands are particularly vulnerable to biological invasions, with freshwater ecosystems expected to experience the most severe impacts. This is especially true if the insular freshwater fauna comprises a large set of near-threatened to critically endangered species. This study assesses the establishment of the pet-traded shrimp Neocaridina davidi and its parasites on the island of la Reunion, a biodiversity hotspot within the Malagasy region. We confirm the establishment of feral N. davidi in two river catchments. Moreover, we confirm the presence of the microsporidian Ecytonucleospora hepatopenaei, an economically and ecologically relevant parasite that might impact a wide range of native species, including those living in brackish and marine environments. Three other microsporidians, two of which are unknown, have also been detected for the first time in N. davidi, raising concerns over possible spillover-spillback events. Therefore, we recommend timely actions to curb the spread of N. davidi and its parasites in an effort to preserve the already endangered native freshwater fauna.