Response of rainbow trout (Oncorhynchus mykiss) to a graded hypoxia following repeated intermittent exposure to chloramine-T

摘要: Abstract The physiological effects of repeated exposure to 9 mg l −1 chloramine-T, a common aquaculture disinfectant for rainbow trout, were examined using graded hypoxic challenge. Using an extracorporeal circulation, continuous measurements blood PO 2 , PCO and pH made correlated with decreasing water . Ventilation amplitude frequency also monitored. Following the challenge, gills removed processed microscopy morphometric determination number branchial mucous cells. Fish treated chloramine-T exhibited higher arterial during hypoxia between 10.1 11.2 kPa when compared untreated controls; there no differences in or two groups. Chloramine-T-treated fish had elevated pre-hypoxic ventilation as controls. However, under hypoxia, control their frequency, whereas chloramine-T-treated did not. Both increased fish. reduced thickness gill epithelial blood-to-water diffusion barrier but numbers cells We suggest that although was cell hyperplasia response exposure, thinning lamellar epithelium sufficient offset any diffusive limitations, thus ensuring gas exchange not adversely affected.