1. Zoological Laboratory, University of Groningen, PO Box 14, 9750 AA Haren, Netherlands
2. 4Station Biologique de la Tour du Valet, Le Sambuc, 13200 Arles, France ()
3. Centre for Mammalian Genetics, Department of Pathology and Laboratory Medicine, Box 10075, University of Florida College of Medicine, Gainsville, FL 32610–0275, USA
4. Department of Histology and Cell Biology, Immunology Section, University of Groningen, Groningen, Netherlands