Enhanced fecundity and parasite release in the first amphipod invader on the Iberian Peninsula

Abstract

Crangonyx pseudogracilis is a North American amphipod recently detected in Portugal and it is the first invasive freshwater amphipod detected in the Iberian Peninsula. The aim of this study was to assess the population structure and its invasion range in this area, but also to assess its pathogen profile and its origin through genetic analyses. Crangonyx pseudogracilis was only found in the lowlands of the Tagus River basin, a restricted area of the three sampled river basins (Tagus, Guadiana and Sado). Only one mitochondrial DNA (mtDNA) gene cytochrome oxidase subunit 1 (COI) haplotype, identical to the one already detected in Europe and in the Lake Charles, USA, was identified. The obtained data show that the studied populations are well-established, have a high female fecundity and a reproduction period extended throughout the year. No parasites were detected in the 236 dissected specimens. The dissimilarity of parasites prevalence to other European invasive populations opens the possibility of a direct introduction from North America but it also does not exclude the possibility of a secondary introduction from another European country.