The dynamics of infection of Diphyllobothrium dendriticum (Nitzsch) and D. ditremum (Creplin) in the char Salvelinus alpinus (L.) in Sweden

Abstract

A total of 654 char, Salvelinus alpinus (L.), from Lake Bjellojaure, Sweden, were examined for plerocercoids of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditrernurn (Creplin, 1825) from September 1969 to December 1974. Plankton samples showed that the dominating copepod species in the lake were Eudiaptomus graciloides (Lilljeborg), Cyclops scutifer Sars and Heterocope appendiculata Sars. E. graciloides passed the winter as adults and C. scutifer as copepodids while H . appendiculata was restricted to a short period in the summer. Copepods occurred in the stomachs in September-October and to a certain extent in April-May, but only cyclopids and Heterocope sp. were found. C.scutifer is proposed to be the main first intermediate host of both D. dendriticum and D. ditremum. The potential final hosts were thecommon gull, Larus canus L., for D. dendriticurn and the black-throated diver, Gavia arctica (L.), for D. ditremum. One common gull was experimentally successfully infected with plerocercoids of D. dendriticum. The parasites showed no seasonal cycle in incidence of infection.

The occurrence of cestode larvae in brown trout after stocking in a large regulated lake in northern Finland

“…In the lakes inhabited only by Arctic char and sticklebacks, a significant proportion of the char population may become piscivorous and heavily parasitised with Diphyllobothrium by transmission from prey fish (Curtis 1983). However, no detailed study of the factors which lead to heavy infection of brown trout and Arctic char (Vik 1957, Halvorsen 1970, Bylund 1972, Henricson 1977, 1978. Curtis 1983, Berube & Curtis 1986, Gustafsson 1996 in some northern lakes with either D. dendriticum or D. ditremum has been undertaken.…”

“…This was also the case in the 1960s, when D. dendriticum had a 90% prevalence in brown trout with an abundance of 100 plerocercoids (Bylund 1966). D. dendriticum and D. ditremum usually share the same copepod and fish species as first and second intermediate hosts (Hickey & Harris 1947, Halvorsen 1966, 1970, Bylund 1973, Henricson 1977, 1978, Curtis 1983, Andersen et al 1987 ditremum IS, however, that the ability of plerocercoids to pass from prey fish to predatory fish is well developed in D, dendriticum while poor in D. ditremum (Vik 1957, Halvorsen 1970, Halvorsen & Wissler 1973. As was seen in the present study in stomach samples of the brown trout, planktonic food decreased with the age of the fish and was replaced by small fishes.…”

“…The latter authors used Henricson's (1977Henricson's ( , 1978 data, and data from others, to suggest that the observed decrease in the mean abundance and the variance-to-mean ratios of Diphyllobothrium dendriticum and D. ditremum in the oldest age groups in Arctic char was the result of host death. In the present data the variance-to-mean ratio decreased in the oldest age group in 1994 material, but the abundance of infection increased, so there was no evidence that the most heavily parasitized individuals were being eliminated from the brown trout population.…”

“…Petersson 1971), since the destruction of littoral bottom fauna forces many fish species to feed more on plankton, including copepods, which are the first intermediate hosts for cestodes. On the other hand, Wisniewski (1958) and Esch (1971) Henricson 1977, 1978, Curtis 1983 trophic lake in Finnish Lapland flowing via the River Berube & Curtis 1986, Gustafsson 1996) in salmonids Paatsjoki into the Arctic Ocean (Fig. 1).…”

Histopathology of Diphyllobothrium ditremum plerocercoids in coho salmon Oncorhynchus kisutch

“…There are reports of mass mortality in salmonids implicating diphyllobothrid plerocercoids (Simms & Shaw 1931, Duguid & Sheppard 1944, Hickey & Harris 1947, Fraser 1960, Hoffman & Dunbar 1961, Becker 1966, Becker & Brunson 1967, Hoffman 1967. More specifically, the importance of Dlphyllobothnum ditremum in parasite induced host mortality has been questioned (Halvorson 1970, Henricson 1977, 1978 Microscopic examination showed hemorrhaging this report is to describe the histopathological changes within tissues invaded by plerocercoids. Liver was the and probable causes of mortality in coho salmon finprimary affected organ with edema and congestion of gerlings dying from D. ditremum plerocercoid parasitsinusoids causing disruption of the muralial architecism when transplanted and experimentally held capture and frank hermorrhaging (Figs.…”