1. University of Jyväskylä, Department of Biological and Environmental Science, Jyväskylä, Finland. e-mail: rmsoimas@jyu.fi
2. Department of Anatomy,Physiology and Cell Biology,School of Veterinary Medicine, University of California, Davis, USA
3. Department of Anatomy,Physiology and Cell Biology,School of Veterinary Medicine, University of California, Davis, USA, and National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI, USA