Laboratory observations on the feeding behavior and feeding rate of the nemertean Procephalothrix simulus

The feeding behavior of the nemertean Procephalothrix simulus and the effects of extrinsic factors on the feeding rates of this nemertean were experimentally studied. Procephalothrix simulus showed a typical macrophagous feeding strategy and consumed various food items. When capturing freshwater Tubifex sp., the nemerteans successfully ingested prey in all attacks, and they did not evert the proboscis in 25% of capture events. When capturing marine Saccocirrus gabrillae, the nemerteans failed to consume prey in more than half of the attacks, and they always everted the proboscis. There was a positive relationship between nemertean body weight and the rate of successful attacks, and a negative relationship between nemertean body weight and the duration of feeding events. The feeding rate of P. simulus increased when the temperature was raised from 5 degrees C to 30 degrees C but was significantly inhibited at 32 degrees C. Food intake was significantly reduced in media diluted to a practical salinity of 20 and 10 and in medium with the salinity elevated to 45. Dark conditions induced higher food intake, but prey density had no significant effect on feeding rate. These results suggest that P. simulus is a predator successfully adapted to the variable environmental conditions of the intertidal habitat.