FISHERY BULLETIN; VOL^ 76. NO. 4 



Figure 5. — Lymphocystis in European plaice, Pleuronectes platessa. (Photograph courtesy of P. Van Banning, Rijkinstituut voor 



Visserijonderzoek, IJmuiden, Netherlands.) 



plaice, Hippogiossoides platessoides, from the 

 Grand Banks of Newfoundland. He suggested sev- 

 eral possible explanations for the outbreak, in- 

 cluding the possibility that the disease is enzootic 

 in the population and may increase in intensity 

 periodically. Earlier, Awerinzew (1911) found an- 

 nual lymphocystis prevalences of 11% in P. flesiis 

 from the Murmansk coast, and Nordenberg ( 1962) 

 found infections as high as 12% in the same species 

 from the Oresund, with some indication of higher 

 prevalence in the warmer months of the year. 

 None of these outbreaks seems to have any ap- 

 parent association with environmental contami- 

 nation. 



Lymphocystis has been reported recently in 

 Baltic herring (C/;//xY/ harengus var. membras ) by 

 Aneer and Ljungberg (1976). Of the 2,629 indi- 

 viduals examined, 14 had gross signs of the dis- 

 ease. The authors pointed out that a number of 

 infections were slight and might easily have been 

 overlooked. It is quite likely that this is the case 

 with other species also. 



The presence of lymphocystis cells in the viscera 

 of herring was noted by Aneer and Ljungberg, and 

 there are several other reports of systemic lym- 

 phocystis infections, particularly that of Dukes 

 and Lawler (1975) in which lymphocystis cells 

 were found in and behind the eyes and in the 

 kidney, spleen, liver, heart, ovaries, and mesen- 



teries of silver perch, Bardiella chtysiira, from the 

 Mississippi coast. 



Lymphocystis has also been recognized in 4.3% 

 ofyellowfin sole, Limanda aspera, sampled in the 

 Bering Sea by Alpers et al. (1977a) and in 68% of 

 winter flounder sampled in 1975 from Casco Bay 

 in the Gulf of Maine (Murchelano and Bridges 

 1976). 



Despite inconclusive attempts to relate lym- 

 phocystis epizootics in flatfish to specific environ- 

 mental factors, including pollutants, there are re- 

 cent observations of the disease in fishes of the 

 Gulf of Mexico that reopen the issue. Christmas 

 and Howse (1970) found lymphocystis in Atlantic 

 croaker and sand seatrout, Cynoscion arenarius, 

 from the Mississippi coast of the Gulf of Mexico 

 and observed that "The pollution load was much 

 gi'eater in estuarine systems where lymphocystis 

 was encountered." However, only 12 infected fish 

 were found in a 10-mo trawling survey with 

 monthly collections at 35 stations, which is not 

 overwhelming evidence for a relationship of the 

 disease to pollution. In a later study, Edwards and 

 Overstreet (1976) reported marked increases in 

 lymphocystis incidences in Atlantic croakers from 

 the Mississippi coast, with as high as 50% infected 

 fish in some trawl collections. Increased preva- 

 lences of another strain of lymphocystis were also 

 observed in silver perch. In a later paper Over- 



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