<i>Salmincola edwardsii</i> (Copepoda: Lernaeopodidae) Parasitic on Southern Asian Dolly Varden, <i>Salvelinus malma</i> <i>krascheninnikova</i>, 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.

Two Copepods <i>Salmincola edwardsii</i> and <i>Salmincola markewitschi</i> (Lernaeopodidae) Parasitic on Chars (<i>Salvelinus</i> spp.) Reared in a Salmon Museum, Northern Japan

“…The specimens of Salmincola C. B. Wilson, 1915 collected from the SSM-reared chars are herein identified as two species, S. edwardsii and S. markewitschi. The morphology of the specimens of each species is identical to that reported for S. edwardsii (Shedko and Shedko 2002;Nagasawa 2020a) and S. markewitschi (Shedko and Shedko 2002;Shedko et al 2005a;Nagasawa 2020c;Nagasawa and Ishiyama 2021). The two species can be distinguished by the following characters: 1) the shape and size of the bulla, i.e., a small subconical anchor with a short manubrium in S. edwardsii (Figs 1A, 2A) but a relatively large mushroomshaped anchor with a long manubrium in S. markewitschi (Figs 1B-D, 3A); 2) the apical armature of the distal segment of the second antenna endopod, i.e., the presence of a prominent process 4 and a powerful hook 1, respectively, in S. edwardsii (Fig.…”

“…Salmincola edwardsii has a wide distribution in the holarctic region and is a parasite of various species of chars (Kabata 1969;Nagasawa 2020a). In Fast East Asia, the species has been reported from southern Asian Dolly Varden in Russia (e.g., Shedko and Shedko 2002;Shedko 2005;Shedko et al 2005a, b;Sokolov et al 2012) and Japan (Shedko and Shedko 2002;Nagasawa 2020a, b;Nagasawa and Kawai 2020).…”

“…The infection site of S. edwardsii is herein reported as the "gills", which is based on information provided by the SSM staff and also on their reports (Anonymous 1989;Takayama et al 1999). However, S. edwardsii is known to use three microhabitats (the wall of the branchial cavity, the gill filaments, and the inner surface of the operculum) in the host's gill region (Nagasawa 2020a), and it is thus better to regard the "gills" as a general infection site of the species.…”

“…According to SSM staff (Takayama et al 1999), a species of copepod, herein identified as S. edwardsii, was constantly found only on southern Asian Dolly Varden during the 1990s after individuals of the fish species were transported alive in 1989 from the Shari River to the SSM. The Shari River is one of the four Hokkaido rivers where S. edwardsii is found (Nagasawa 2020a;Nagasawa and Kawai 2020). Thus, it is most likely that S. edwardsii was brought into the SSM along with southern Asian Dolly Varden from the Shari River and thereafter maintained its population using this fish species during the 1990s.…”

Relative importance of host‐dependent versus physical environmental characteristics affecting the distribution of an ectoparasitic copepod infecting the mouth cavity of stream salmonid

“…(but not other salmonids) and their infections commonly occur in the mouth cavity but not in the gill tissue or on the body surface. To date, five species of the genus Salmincola have been recorded from Japan: S. californiensis (reported as S. yamame in Hoshina & Suenaga, 1954;Hoshina & Nishimura, 1976;Nagasawa & Urawa, 2002), S. carpionis (reported as S. falculata in Yamaguti, 1939;Nagasawa et al, 1995;Nagasawa & Urawa, 2002;Nagasawa & Sakaki, 2020), S. stellata (Hiramatsu et al, 2001;Nagasawa et al, 1994;Nagasawa & Urawa, 1991), S. edwardsii (Nagasawa, 2020a(Nagasawa, , 2020bNagasawa & Kawai, 2020), and S. markewitschi (Nagasawa, 2020c;Nagasawa & Ishiyama, 2021). S. carpionis and S. markewitschi mainly infect the mouth cavity of the genus Salvelinus (Kabata, 1969;Nagasawa et al, 1995;Shedko & Shedko, 2002).…”