Particle capture by Daphnia: evidence from high-speed microcinematography

Murray-Darling Freshwater Research Centre

MDFRC item.

Following feeding experiments, the distribution of algal cells on the trunk limbs of Daphnia carinata was almost exclusively on the setae and setules of the first two thoracic limbs (I and II). Traditionally, the third and fourth limbs (III and IV) were considered the sites of particle collection by filtration. High speed 16mm cinematography (250 f.p.s, Lo-Cam camera, Wild M – 400 photomacroscope) was used to determine the function(s) of the limbs, particularly whether III and IV were functioning as sieves. Polystyrene beads (5, 9 and 18 µm) and algae (Ankistrodesmus and Scenedesmus) were fed to D. carinata. All particles were handled by limbs I and II, with no evidence of a sieving function by III and IV. There was evidence from the film that the latter limbs are involved in maintaining the currents needed for particle extraction. The limb movements involved sequences that simple filtration is not an adequate description of the process.