Periwinkles of the genus Littorina have been used as a model organisms for microevolutionary, ecological, and physiological study. Nevertheless, the exact mechanisms which restrict gene flow between closely related species of this genus are still unknown. We assume the presence of postmating prezygotic reproductive isolation (PMPZ) which function through interactions of male-female pairs of molecules (Lobov et al., 2019).</p><p>None of such molecules was described for Caenogastropoda (and internally fertilized molluscs in general). Thus, we started with the identification and analysis of such proteins. We found several candidate-proteins by the proteomics analysis of male's reproductive tissues (Lobov et al., 2015, 2018, 2020).</p><p>According to this, we followed our search by analysis of species-specific female reproductive proteins, possibly involved in PMPZ through interaction with proteins described by us previously. In this study, we applied transcriptomics methods to the comparative analysis of oviducts tissues from L. obtusata and L. fabalis closely related species.