Species identification of recently established alien freshwater crayfish in Niigata Prefecture, Japan, with implication of their origin based on ectosymbiotic branchiobdellidan composition

Abstract

Abstract Based on the morphological examination of the specimens, the recently established alien crayfish in Niigata Prefecture was identified as Pacifastacus leniusculus (Decapoda: Astacidae). Ectosymbiotic branchiobdellidans on the crayfish were composed of a single species, Sathodrilus attenuatus. (Annelida: Clitellata). Such a combination of crayfish and ectosymbionts suggests that the Niigata population has been derived from populations in the upper course watershed areas of Fukushima Prefecture or by illegal introduction.