Juvenile survival of a planktonic insect: effects of food limitation and predation |
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Authors: | JANET M. FISCHER MARIANNE V. MOORE |
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Affiliation: | Department of Biological Sciences, Wellesley College, Weltesley, MA 02181–8283, U.S.A |
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Abstract: | - 1 An experiment was conducted to investigate potential impacts of food limitation and copepod predation on juvenile survival of Chaoborus purtctipennis. We tested the hypotheses that: (i) juvenile survival of Chaoborus is influenced more by copepod predation than by starvation in a productive environment, and (ii) food limitation and predation interact to affect survival.
- 2 Effects of food concentration (approximately 800, 1400 and 2300 microzooplankton 1-?1) and predator density (0, 1 and 2 Mesocydops edax 1-?1) on Chaoborus development and survival were evaluated using a 3 × 3 factorial design. Jars containing lake water, the appropriate food and predator treatments, and two Chaoborus (<12h old) were rotated on a plankton wheel at 25°C. Survival and developmental stage were monitored daily until all individuals had either died or moulted to instar II.
- 3 Predation by Mesocydops was the major source of mortality, causing 87.5% of Chaoborus deaths over all treatments. Chaoborus mortality was significantly higher in treatments with Mesocydops (67–100%) than in predator-free treatment (0–13%).
- 4 Development time was significantly longer in the low-density food treatment than in the highest food treatment.
- 5 No significant interaction between food limitation and predation was detected.
- 6 These results suggest that predation by copepods may limit recruitment of juvenile Chaoborus in productive lakes.
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