Glochidiosis of salmonid fishes. IV. Humoral and tissue responses of coho and chinook salmon to experimental infection with Margaritifera margaritifera (L.) (Pelecypoda: Margaritanidae)
Meyers, T.R.; Millemann, R.E.; Fustish, C.A.
Journal of Parasitology 66(2): 274-281
1980
ISSN/ISBN: 0022-3395 PMID: 7391868 Document Number: 158413
Coho salmon (Oncorhynchus kisutch) are more resistant than chinook salmon (O. tshawytscha) to experimental infection with the glochidia of the freshwater mussel M. margaritifera. Histological sections of gills from coho salmon 16 h postinfection (p.i.) showed that parasite encystment either did not occur or had progressed incompletely, which accounted for the loss of many glochidia from the gills. The remaining encysted glochidia were sloughed within 2 days (p.i.) by a welldeveloped hyperplasia. On chinook salmon, the parasites developed normally with no sloughing or hyperplasia. Analysis of blood samples taken from coho salmon at intervals during the infection showed significant increases in hematocrit, Hb, mean corpuscular volume (MCV), mean corpuscular Hb (MCH) and leukocyte numbers when compared with control fish. In infected chinook salmon only the hematocrit, erythrocyte numbers, and MCV increased while the MCHC mean corpuscular Hb concentration decreased. Total plasma protein increased in coho salmon but decreased in chinook salmon during infection. Glochidial antibodies were demonstrated in the blood plasma of coho and chinook salmon 8-12 wk, p.i. Fewer glochidia attached to the excised gills of coho salmon than to the gills of chinook salmon. In vitro survival time of parasites in mucus and plasma from coho salmon was less than in chinook salmon fluids.