An alien ectosymbiotic branchiobdellidan (Annelida: Clitellata) adopting exotic crayfish: a biological co-invasion with unpredictable consequences

Invasive alien species present a global threat to biodiversity, particularly where pathogens and symbionts are involved. Branchiobdellidans are clitellate annelids with an obligate ectosymbiotic association primarily on astacoidean crayfish. There are several examples of branchiobdellidan species adopting a geographically exotic host where endemic and exotic crayfishes cohabit the same water body. The first records of a western North American branchiobdellidan, Xironogiton victoriensis , adopting the eastern North American crayfish, Procambarus clarkii , in 2 river basins in Spain provide further evidence of the ectosymbionts’ tolerance to adopt an exotic host. Given worldwide translocation…