1 Developmental Biochemistry, Biocenter, Am Hubland, University of Würzburg, 97074 Würzburg, Germany; The Xiphophorus Genetic Stock Center, Texas State University, 601 University Drive Centennial Hall 419, San Marcos, TX-78666, USA. Electronic address: phch1@biozentrum.uni-wuerzburg.de.
2 Department of Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany.