日光市で発見されたニホンザリガニ個体群の由来、および大正時代に北海道から本州に持込まれた個体に関する宮内庁公文書等に基づく情報 Origin of the freshwater Japanese crayfish Cambaroides japonicus in Nikko, Honshu, Japan and information on crayfish transported from Hokkaido based on archives from the Imperial Household Agency

The known distributional range of the Japanese crayfish, Cambaroides japonicus（ De Haan, 1841（）Crustacea,Decapoda, Cambaridae） is restricted to north part of Japan including Hokkaido, Aomori and northern parts of Akitaand Iwate Prefectures. Recently a new population of this species was discovered from natural habitat in Tamozawa,Nikko, Tochigi Prefecture, Centaral Honshu, Japan. Present study examined origin of the Nikko population based on thecomposition of symbiotic crayfish worms（ Annelida, Clitellata, Branchiobdellida） as well as the crayfish morphologies（rostrum, telson and annulus ventralis）. Three species of crayfish worms, Cirrdrilus cirratus Pierantni, 1905, C. inukaii（Yamaguchi, 1934）, and C. ezensis（ Yamaguchi, 1934） were detected from the Nikko crayfishes, all of which are knownto endemic to Hokkaido. Morphological characteristics in the crayfishe corresponded to those in Hokkaido population.　　Some documents and old archives （ca. 1900） in the Archivs and Mausolea Department, Imperial HouseholdAgency, Japan suggest that many individuals of C. japonicus had been transported to the Nikko Tamozawa Imperial Villafrom Hokkaido, and they were used as foods for the royal family. A map in an old archive indicates that there was anaquarium near the kitchen of the Imperial Villa. Consequently, it is highly probable that the present Nikko population ofC. japonicus is derived from introduced individuals for foods from Hokkaido.