engleski

Reproductive preferences of the bitterling Rhodeus amarus (Bloch, 1782) among five bivalve species from the family unionidae.

The reproductive cycle of bitterling includes oviposition in a live freshwater bivalve from the family Unionidae, with the bitterling eggs and embryos developing inside the shell. Although the number of native freshwater mussels in Europe is declining, in Croatia, the bitterling is currently very abundant and is widely distributed throughout the Danube drainage. Furthermore, it is considered invasive at several sites in the Adriatic basin. On the other hand, Sinanodonta woodiana is an invasive freshwater mussel that has entered Croatia and is rapidly expanding its range. We conducted an experiment to test the reproductive preferences of bitterling among five species of freshwater mussels (four native: Anodonta anatina, Unio crassus, U. tumidus and U. pictorum ; and one invasive: Sinanodonta woodiana). Four males and 16 female bitterlings were kept in an aquarium with four equal territories, each containing all five investigated mussel species. After 20 days, mussels were recovered and the number of eggs and embryos in the gills was counted. A total of 319 eggs and embryos were recovered with most (95) in A. anatina, followed by U. crassus (89), U. tumidus (80) and U. pictorum (55). Not a single egg or embryo was found in the invasive S. woodiana. These results indicate a future potential threat for bitterling survival, as the suppression of native mussel species by the competing invasive species could hinder its reproduction.

invasive freshwater mussel, bitterling reproduction

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