1Aquaculture and Fish Nutrition Research Group, School of Marine Science and Engineering, Marine Institute, University of Plymouth, Plymouth, Devon, PL4 8AA, UK
2Swiss College of Agriculture, CH-3052 Zollikofen, Switzerland
3Alltech Inc., GR-28200 Lixouri, Cephalonia, Greece
4Electron Microscopy Centre, University of Plymouth, Plymouth, Devon, PL4 8AA, UK