B. Hansen, T. Wernbergmoller, L. Wittrup-1997
Journal of Experimental Marine Biology and Ecology, 215 (2): 217-233 (from Current Contents)
Abstract:
A complete particle retention spectrum for the grazing of Brachionus plicatilis on phytoplankton of different cell size revealed optimal grazing on an algae (Tetraselmis suecica) with an equivalent spherical diameter (ESD) of 8.3 mu m. Furthermore, although grazing suboptimally, the rotifer grazed with an equal efficiency (60%) on two different algae Rhodomonas baltica (R.b.) and Thalassiosira fluviatilis (T.f.) with equivalent spherical diameters of 6.5 mu m and 12.9 mu m, respectively, when they were offered one alga at a time. These two algal species were in size positioned symmetrically in the bell shaped curve around the optimal prey size for the rotifers. In mixtures of these two algal species the total grazing on the two algae remained equal regardless of the ratio between the two species in the mixtures. The functional responses to the two algal species offered separately resulted in similar maximum ingestion (I max) but different half saturation constants (K m).
In order to describe the growth efficiency for the rotifer, a 7 day growth experiment with the haptophyte Rhodomonas baltica was conducted at 15 degrees C with 7 different food concentrations. The specific growth rate vs. food availability followed Monod kinetics with a maximum specific growth rate (G(max)) = 0.49/day and a K m = 2.25 ppm (R.b. 12 150/ml). The mean carbon content of the individual rotifers vs. algal concentration also followed a Monod curve. Body length could be related to carbon by C (ngC) = 1.06 x 10( 4) L (mu m)(2.74). The carbon density of the rotifers were 0.11 pgC mu m( 3). The carbon yield (specific growth rate vs. specific ingestion rate) was 0.29. The maintenance food concentration was 1.02 ppm (R.b. 5000/ml). The rotifer lost 0.22/day when starved. The high specific growth rate and the high saturation food concentrations as well as the high energy requirement during starvation supports the idea that the rotifer follows a life strategy with a fast growth response.
(Roskilde Univ Ctr, Dept Chem & Life Sci, POB 260, DK-4000 Roskilde, Denmark)
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