No abstract

Chum salmon Oncorhynchus keta were injected with erythrocytic necrosis virus (ENV) to study the physiological and hematological consequences of ENV infection. Infected and control fish were held in pathogen-free seawater and sampled for 5 weeks. Physiological tests included measures of plasma cortisol, glucose, protein, and osmolality; blood lactic acid; and liver glycogen. In general, ENV-infected fish had lower plasma glucose and blood lactic acid, and higher liver glycogen concentrations than did control fish. Hematological tests included red and white blood cell (RBC and WBC) counts, hematocrit, measurement of blood hemoglobin concentration, and a determination of erythrocyte fragility. Infected fish had lower RBC counts, hematocrits, and hemoglobin concentrations; higher WBC counts; and less fragile erythrocytes than did control fish. The hematology data indicated that erythrocytes of infected fish had higher mean corpuscular volume, depressed mean corpuscular hemoglobin concentration, and slightly lower mean corpuscular hemoglobin. Erythrocytic inclusions were observed in the cytoplasm of RBCs from infected fish. The infection progressed steadily through week 4, after which the fish appeared to begin recovering. In a second study, fish were infected with ENV for 3 weeks, and recovery from a stress challenge test was measured. Plasma glucose concentrations and osmolality were higher in infected fish, whereas plasma cortisol and blood lactate were only slightly elevated. These studies indicate that chum salmon withstood the effects of ENV infection without irreversible physiological consequences. However, when subjected to a stress challenge test, infected fish recovered more slowly than control fish and had increased osmoregulatory difficulties.

The occurrence, prevalence, seasonality and histopathological progression of a cellular disorder, thought to be a haemic neoplasm, were studied in subpopulations of Mytilus edulis inhabiting different sites in Yaquina Bay, Oregon, from 1976-1981. There were significant differences in the occurrence of the disorder that were related to geographical location. In the subpopulation with the highest levels of the disease, the prevalence rates ranged from 0 to 20% with a 5-year mean of 9-8%. There was a statistically significant relationship between prevalence and season. During the 5-year study period, there was a consistent pattern characterized by highest prevalences during January to March followed by a period of decline to lower levels during the summer and early autumn, after which there was an increase. Data analyses revealed that there was no seasonal histopathological progression of the disorder. Numbers of stage 1 (early), 2, 3 and 4 (advanced) cases were not related to season but occurred in a random manner throughout the entire year.

No abstract

No abstract