Closely related species of periwinkles of the genus Littorina, especially, L. saxatilis, 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). Moreover, L. saxatilis is oviviparous, while other species from " saxatilis" group (L. arcana and L. compressa) form clutches.</p><p>Nevertheless, the differences in transcriptomes of oviducts of these closely related species were not investigated yet. Thus, here we comparative RNA-seq analysis of oviducts transcriptomes of Littorina saxatilis, L. compressa and L. arcana.