| Adult specimens of the invasive crayfish Pacifastucus leniusculus were collected from the Tone River basin between September 2009 and January 2010. Ectosymbiotic crayfish worms (Annelida、 Clitellata、 Branchiobdellidae) were found on the crayfish and all specimens were identified as Sathodrilus attenuatus、 which outside of its home range in North America occurs only in the Hokkaido and Fukushima Prefecture populations of P. leniusculus; thus suggesting that P. leniusculus in the Tone River basin was introduced from Hokkaido or Fukushima Prefecture. |