External Egg Membrane Characteristics of Landlocked Fall Chinook Salmon Eyed Eggs Treated with Hydrogen Peroxide or Formalin

Abstract

AbstractThis study examines the microscopic characteristics of external egg membranes from eyed eggs of landlocked fall Chinook salmon Oncorhynchus tshawytscha treated with formalin (1,667 mg/L) or hydrogen peroxide (700 mg/L) for 15 min daily until hatching. Just before the start of hatching, the internus layer became significantly less differentiated in the membranes of eggs treated with hydrogen peroxide compared with those in the formalin treatments or untreated controls. There were no significant differences among the treatments in total membrane thickness, pore canal height, basal layer height, pore canal width, and the number of pore canals per 50‐μm lengthwise segment along the membrane. Overall membrane thickness (externus and internus layers combined) averaged 51.5 μm during the test period. Thickness of externus averaged 0.69 μm, nearly two times that reported previously for nonlandlocked Chinook salmon.