In the search for new strategies to fight schistosomiasis, the unique reproductive biologyofSchistosoma mansonihas come into the focus of research. The development of thegonads and the ability of egg production are fundamental not only for continuing the lifecycle but also for pathogenicity. Previous studies of schistosome biology demonstrated aninfluence of pairing on gonad development of the female and on gene expression profilesin both genders. Due to the limited access to specific tissues, however, most of thesestudies were done at the level of whole worms neglecting individual tissues that may betargets of pairing-dependent processes. Recently, we established a protocol allowing theisolation of testes and ovaries from adultS. mansoni. Here, we describe tissue-specificqRT-PCR analyses comparing transcript levels of selected genes on the basis of RNAfrom gonads and whole worms. Gene expression in ovary and testes was in some casesfound to be significantly influenced by pairing, which was not traceable in whole worms.Among the candidate genes identified as regulated by pairing in gonads were the frizzledhomolog SmFz1 and the two fibroblast growth factor receptor homologs SmFGFR-A andSmFGFR-B. First functional characterizations were done, including comparative qRT-PCRanalyses,in situ-localization experiments, heterologous expression inXenopusoocytes(SmFGFR-A/B), and inhibitor studies using the Fz/Dvl-pathway inhibitor 3289-8625, orBIBF1120 blocking FGFR-signaling. Besides confirming gonad localization and receptorfunctions, inhibitor-induced phenotypes were observedin vitrosuch as decreased eggproduction as well as drastic effects on gonad differentiation, morphology, embryogenesis,and survival of adult worms. In summary, these results emphasise the usefulnessof tissue-specific qRT-PCRs for selection of candidate genes with important roles inreproduction, allowing subsequent studies to determine their suitability as drug targets.