Salmincola edwardsii (Copepoda: Lernaeopodidae) Parasitic on Southern Asian Dolly Varden, Salvelinus Malma Krascheninnikova, from Hokkaido Island, Japan, with the Southernmost Distribution Record of the Copepod in Asia

Abstract

Females of the lernaeopodid copepod Salmincola edwardsii (Olsson, 1869) were found parasitizing the gill area of southern Asian Dolly Varden, Salvelinus malma krascheninnikova Taranetz, 1933, from four rivers (Rusha River, Rausu River, Shari River, Shibetsu River) in and near the Shiretoko Peninsula, eastern Hokkaido Island, Japan. The females are briefly described as the first record of S. edwardsii from Hokkaido Island and the southernmost distribution record for the species in Asia. The branchial chamber was the most frequently used site for attachment by the females, followed by the gill filaments and the inner surface of the operculum. The overall prevalence of infection was 42.1%, and intensity ranged from 1 to 6 (mostly 1 or 2). The species was not collected from the central and western regions of Hokkaido Island, and the restriction of its distribution to eastern Hokkaido Island is discussed in terms of anadromy of the host species. The impact of global climatic warming on the Hokkaido populations of S. edwardsii is also discussed.