The reproduction of three species of mud snails, Hydrobia neglecta, H. ulvae and H. ventrosa is studied under constant conditions of various temperature/salinity combinations and in seven field populations. Under otherwise constant conditions the egg production of H. neglecta increases with temperature (4-24°C), while it decreases in H. ulvae and H. ventrosa. All species show a general peak in reproductive activity around 20 ‰ salinity. In H. neglecta egg production is retarded at low salinity, which may explain the absence of the species in the inner Baltic Sea. All natural populations exhibit peak reproductive activity during May-June, and total numbers of eggs compare well with the values obtained under constant conditions. |
