FIGURE 1. — Sea lamprey erythrocytes with PEN lesions. In- 

 fected cells show characteristic chromatin condensation with 

 evidence of nuclear vacuolization. From a female lamprey 80 

 cm in total length from the Coopers Mills Fishway, Coopers 

 Mills. Me., on 26 May 1980. Sea lamprey erythrocytes are 

 rounded in shape in contrast to most other fish species which 

 have elliptical shaped red cells. 



i 



* 



* 



FIGURE 2. — Red acidophilic inclusions are occasionally seen in 

 PEN infected sea lamprey erythrocytes. From a female lamprey 

 67.8 cm in total length from the Sheepscot Pond Fishway, 

 Palermo. Me., on 9 June 1978. 



Discussion 



microscopy. Consequently, viral etiology of the 

 condition still remains to be confirmed. 



Fish obtained from lakes where alewives spawn 

 have shown typical PEN lesions (Sherburne, un- 

 publ. data), but whether alewives contribute to 

 this is unknown. MacMillan and Mulcahy (1979) 

 reported transferring VEN to chum salmon, 

 Oncorhynchus keta, and brook trout, Salvelinus 

 fontinalis, by waterborne virus. Perhaps infected 

 anadromous species can transmit PEN to fresh- 

 water species via body fluids such as urine and 

 reproductive products as well as by direct contact. 



Lampreys could conceivably transmit PEN to a 

 variety of marine and freshwater species because 

 of their feeding habits, their diversity of prey, 

 and their ability to become adapted to an entirely 

 freshwater environment. The high prevalence of 

 infection and the low intensity of infection sug- 

 gest that lampreys might readily spread the in- 

 fection without suffering a high mortality rate 

 from PEN. 



I prefer to use the term PEN in species where 

 the cellular pathology has not yet been confirmed 

 as associated with a virus, and viral erythrocytic 

 necrosis (VEN) after confirmation. By light mi- 

 croscopy, PEN lesions of lamprey red cells resem- 

 ble those of VEN-infected Atlantic cod. As with 

 alewives, Alosa pseudoharengus, (Sherburne 

 1977) and smelt, Osmerus mordax, (Sherburne 

 and Bean 1979), lampreys have a relatively high 

 percentage of individuals affected with PEN, but 

 individual infections are very light. 



The blood of the sea lamprey must be examined 

 by electron microscopy to determine if the PEN 

 seen is an ICDV infection. Unfortunately, the 

 individual infections observed in this study were 

 so light as to preclude their detection by electron 



Literature Cited 



APPY, R. G., M. D. B. BURT, AND T. J. MORRIS. 



1976. Viral nature of piscine erythrocytic necrosis (PEN) 

 in the blood of Atlantic cod iGadus morhua). J. Fish. 

 Res. Board Can. 33:1380-1385. 

 BIGELOW, H. B., AND W. C. SCHROEDER. 



1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. 

 Serv, Fish. Bull. 53:1-577. 

 EVELYN, T. R T., AND G. S. TRAXLER. 



1978. Viral erythrocytic necrosis: natural occurrence in 

 Pacific salmon and experimental transmission. J. Fish. 

 Res. Board Can. 35:903-907. 

 EVERHART, W. H. 



1976. Fishes of Maine. 4th ed. Maine Dep. Inland Fish. 

 Wildl., Augusta, Me., 96 p. 

 HUBBS, C. L., AND K. F. LAGLER. 



1949. Fishes of the Great Lakes region. Cranbrook Inst. 

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543 



