[1] Univ Oviedo, Dept Morfol & Biol Celular, Asturias, Spain
[2] Univ Oviedo, IUOPA, Oviedo, Spain
[3] Univ Texas, Hlth Sci Ctr, Dept Cellular & Struct Biol, San Antonio, TX 78284 USA
[4] Univ Gottingen, Inst Zool & Anthropol, D-3400 Gottingen, Germany