Experimental study of suspension-feeding activity in the serpulid polychaete Ditrupa arietina (O.F. Müller)

As time spent feeding can be an index of the feeding intensity, we attempted to describe the filtering activity in the suspension-feeding polychaete Ditrupa arietina. This description was based on the detection of the opening of the gill-crown by an automated image analysis system. The common pattern of activity could be described as the succession of filtering events and resting periods of which the number and the mean duration differed greatly from one worm to another. Filtering activity in D. arietina was neither a continuous process nor even a process having a particular rhythm. Within a same batch of worms, total filtration durations could represent between 12.5 and 87.5% of the total experimental time. Despite a strong inter-individual variability, our results showed the existence of pronounced seasonal variations in the activity of the gill-crown. In May, worms spent less than 25% of time feeding compared to more than 50% during the rest of year. These temporal changes appeared to result from the physiological state of the worms (reproductive period and ageing) at the time of the experiment.