Factors affecting swimming speed in the rotifer Brachionus plicatilis

This study examines the swimming speed in amictic females of Brachionits Plicatilis in laboratory cultures. Five different stages were examined: recently hatched females, juveniles, adult non-ovigerous females, ovigerous females with I attached egg and ovigerous females with 2 attached eggs. We tested the speed at two temperatures, 15 degrees C and 25 degrees C, and two feeding conditions, presence and absence of microalgal cells. An automated motion analysis system was used to measure speed which was then video recorded. Swimming speed (mu m s(-1)) increased with increasing body size. There was a slight decrease in the speed of adult females as the number of attached eggs increased. Swimming activity was higher at 25 degrees C than at 15 degrees C and in the absence of food than if microalgae were present. Average values under the different experimental conditions ranged between 500 pm s(-1) for the recently hatched and fed females and 1500 mu m s(-1) for the adult non-ovigerous females in the absence of microalgae. Mass-specific swimming speed decreased with body mass increase.