Histological Adaptation to Thermal Changes in Gills of Common Carp Fishes Cyprinus carpio L.

Investigations were carried out on the gill tissues of common carp Cyprinus carpio L. exposed to high levels 31oC, and low levels 18oC of temperature for a total period of successive of 10 days. The histological study of the gill sections of this fish species showed marked histological lesions, include hyperplasia and hypertrophy of the respiratory epithelium, bloody congestion with hemorrhage and abundance of mucous substance, this at high temperature, while at low temperature also showed hyperplasia, shrinkage of blood vessels, fusion of secondary lamellae, cellular atrophy, damage and lamellar disorganization. Lesions were comparatively most severity at low temperature.