The feeding biology of Hydrobia ventrosa (Montagu). I. The assimilation of different components of the food

The assimilation efficiencies for 7 species of diatoms, two of blue-green algae, and one bacterium have been measured in the deposit-feeding prosobranch Hydrobia ventrosa (Montagu). Two methods have been used, a chemical and a radiotracer one.The results of the first method were difficult to evaluate due to the fact that the time taken to clear the gut is ill-defined. The second method gave more consistent results.All diatoms are assimilated efficiently (60–71 %) as is the bacterium (about 75 %). The blue-green algae are less efficiently utilized; an Oscillatoria sp. was assimilated with an efficiency of about 50 % whereas a Chroococcus sp. was only assimilated with an efficiency of 8 %. It is concluded that resource partitioning based on differential utilization of micro-organisms cannot play an important rôle in the co-existence of Hydrobia ventrosa with other deposit-feeders.