Structural Alterations in the Gill of the Red Sea Bream, Pagrus major, Exposed to the Harmful Dinoflagellate Cochlodinium polykrikoides

Structural Alterations in the Gill of the Red Sea Bream, Pagrus major, Exposed to the Harmful Dinoflagellate Cochlodinium polykrikoides

The effects of Coehlodinium polykrikoides on the gill of red sea bream, Pagrus major, were examined to clarify the ichthyotoxic mechanisms of this plankton species. The gill of fish exposed to dense blooms over 3,000 cells/mL for 24 h showed severe epithelial separation: a severe edema was found in the secondary lamellar epithelium and interlamellar regions of primary filament. In addition, lipid peroxidation of gill tissue in Coehlodinium-exposed fish was about 2.5 times higher than that of control. The composition of glycoproteins in the gill mucus of Coehlodinium-exposed fish was also changed. These results suggest that the loss of structural integrity of cell membranes in fish gill may be deeply involved in fish death by C. polykrikoides.