Host selection and Change of Skin Surface for Spawning Adaptation of Two Sympatric Bitterling Species

Bitterlings (subfamily Acheilognathinae) are small cyprinid fishes with specialized spawning habits; they deposit their eggs on the gills of freshwater mussels using their ovipositors. This study on spawning host-selection in two sympatric bitterling species, Acheilognathus macropterus and Rhodeus ocellatus , was conducted in the Bulgapcheon Stream, Korea, where four mussel species coexisted. After analyzing the four mussel species immediately after spawning, we discovered that the two bitterlings used only two mussel species as their spawning hosts, Anodonta arcaeformis and A. were predominantly found in the suprabranchial chambers of the two mussel species, and the larvae were even seen in their gill chambers. In contrast, the embryos and larvae of were almost exclusively found in one region of the mussel gill chamber, unlike the two regions used by . The present study indicate that the relationships between bitterlings and their hosts are closely associated with several factors such as ovipositor length, egg sizes, egg adhesiveness, and the coexisting mussels’ ecological habitat.