Effects of rotifers and ciliates on the growth and survival of Daphnia |
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Authors: | Wickham, Stephen A. Gilbert, John J. Berninger, Ulrike-G. |
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Affiliation: | 1Dartmouth College, Department of Biological Sciences, 6044 Gilman Laboratory Hanover, NH 03755-3576, USA 2Max-Planck-Institut für Marine Mikrobiologie BITZ, Fahrenheitstrasse 1, D-2800 Bremen 33, FRG 3Present address: Max-Planck-Institut für Limnologie Postfach 165, D-2320 Plön, FRG |
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Abstract: | Daphnia can suppress ciliates and rotifers through predationand interference competition, but it is not known whether thisproduces any direct benefit to Daphnia. We conducted survivorshipand cohort lifetable experiments to determine whether Daphniacan utilize ciliates and rotifers as food. Three species ofoligotrich ciliates (Halteria grandinella, Strobilidium gyransand Strobilidiumvelox) and one rotifer (Keratella cochlearis)were used. Lifetable experiments were conducted with a basallevel of algae (Cryptomonas sp.), plus either ciliates or rotifers,while survivorship experiments had only the rotifers or ciliates.Densities of 30 H.grandinella ml1, 50 S.gyrans ml1and 15 S.velox ml1 enhanced Daphnia pulex's populationgrowth rate 3550% over controls with only algae. TenS.gyrans ml1 did not produce a significant change inDaphnia's growth rate. Densities of 100 and 300 K.cochlearis1 increased Daphnia population growth rates by II and10%, respectively. Both 10 and 50 S.gyrans ml1 enhancedDaphnia's survivorship compared to starved controls, but neither100 nor 300 K.cochlearis l1 enhanced its survivorship.The amount of enhancement of Daphnia growth rates by rotifersand ciliates is roughly proportional to the death rates imposedby Daphnia. The death rate imposed by Daphnia on rotifers isa function of both algal density and Daphnia size. Per unitbiomass, neither ciliates nor Keratella appear to be as nutritiousfor Daphnia as is Cryptomonas. |
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