SHERBURNE: ERYTHROCYTE DEGENERATION IN HERRING 



red cells in contrast to the 20% immature red 

 cells normal for wild herring; microcytic eryth- 

 rocytes less than one-half normal size; and 

 varying degrees of anisocytosis and poikilocy- 

 tosis. The affected red cells have some charac- 

 teristics of piscine erythrocytic necrosis (PEN) 

 as described by Laird and Bullock (1969), in a 

 cod, Gddus morhua, from Passamaquoddy Bay. 

 These authors associated the PEN in cod with 

 viruslike particles. Walker (1971; pers. comm., 

 July 1972) has confirmed the viral nature of 

 PEN in cod by electron microscopy. He also 

 confirmed the correlation of nuclear lesions as 

 described by Laird and Bullock with the pre- 

 sence of cytoplasmic viroplasm and virions. Al- 

 though I believe the inclusion bodies in herring 

 can be explained as a physiological response to 

 environmental stress, the possibility of their 

 viral nature has not been ruled out and requires 

 further investigation. 



5 10 15 20 25 30 35 40 45 50 55 60 

 HEMATOCRIT, VOLUMES PERCENT 



Figure 8. — Relation of hematocrit values to hemoglobin 

 concentrations in captive herring during late winter, 

 1965. 



A relationship appears to exist between inclu- 

 sions in herring erythrocyte? and stress factors, 

 especially temperature extremes. Except in one 

 instance when inclusions occurred in herring 

 from water of 2°C, all herring from Boothbay 

 Harbor (lat 43°50'N, long 69°40'W) having in- 

 clusions were taken from seawater temperatures 

 of 13.8°C or above. At a temperature of 16°C, 

 96% of a sample of herring were affected with 

 inclusions. Inclusions were found in 2 of 90 

 herring sampled from the Passamaquoddy Bay 

 area (lat 45°00'N, long 67°00'W). These her- 

 ring were taken from a seawater temperature 

 of 9.8°C, the highest temperature sampled in 

 that area. During the months of June and July 

 water temperatures in the Passamaquoddy Bay 

 area have, over a number of years, averaged 

 approximately 4°C lower than in the Boothbay 

 Harbor area (Colton and Stoddard, 1972). 



The incidence of inclusions within a popula- 

 tion can change rapidly, apparently with chang- 

 ing environmental conditions, and they are ca- 

 pable of affecting a high percentage of herring 

 within a population in a very short time. As an 

 example, the wild herring on 8 July from Booth- 

 bay Harbor had a 6.6% incidence of inclusions 

 (5/76); however, 2 .weeks after herring from 

 this population were placed in the laboratory 

 tanks, 96% of the herring sampled (24/25) were 

 affected with inclusions, and over 90% of the 

 red cells in individual herring contained these 

 bodies. 



These bodies, associated with erythrocytic de- 

 generation characterized by necrotic nuclei, a 

 ballooning degeneration of the red cells and the 

 appearance of unusual cells in the blood, may be 

 indicative of stress situations for immature her- 

 ring in the wild. If the stress factors causing 

 these inclusion bodies affect enough herring, 

 they could conceivably have an adverse affect on 

 the population structure endemic to certain 

 areas. The erythrocytic degeneration found in 

 herring may be due to a viral infection as de- 

 scribed in other fishes by Laird and Bullock 

 (1969) and confirmed by Walker (1971). The 

 occurrence of such a viral infection in epidemic 

 frequency would certainly be no less important 

 to our understanding of fluctuations in abun- 

 dance of herring populations. 



133 



