Expression of Sodefrin Precursor Factor. Asterisks show the male breeding glands. (a) PCR-Amplification of SPF precursors in the male cheek and cloaca, female cheek and cloaca, and male skin, gonads and liver, using 11 different primer combinations. The primer combinations are cross-referenced in Additional file 1. For combinations 2–8 and 9–11, comparable results were obtained and only one representative gel is shown. The elongation factor 1-alpha gene (EF1-a) was used as control. (b) Number of recovered SPF transcripts in breeding glands and other tissues of Notophthalmus viridescens.