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Vol. 48 No. 6, 2009
Impacts of Predation by the Copepod, Mesocyclops pehpeiensis, on Life
Table Demographics and Population Dynamics of Four Cladoceran Species:
a Comparative Laboratory Study
Jiang-Shiou
Hwang1,*, Ram Kumar2, and Chung-Su Kuo1
1Institute
of Marine Biology, National Taiwan Ocean University, Keelung 202, Taiwan
2Ecosystem Research Lab, Acharya Narendra Dev College
(University of Delhi), Govindpuri, Kalkaji, New Delhi 110 019, India
Jiang-Shiou
Hwang, Ram Kumar, and Chung-Su Ku (2009) Predation is a major source of prey
mortality in which the goal of the predator is to maximize the
efficiency with which it can ingest its prey while that of the prey is
to develop strategies to minimize mortality due to predation.
Copepods are dominant invertebrate predators in tropical freshwater
ecosystems. The evolutionary responses to copepod predation
pressures are not known in tropical systems. The predatory
copepod, Mesocyclops pehpeiensis,
is numerically abundant and exerts major predation pressures on
different cladoceran species in tropical and subtropical freshwater
systems. We investigated in the laboratory the responses of 4
cladoceran species: Scapholeberis
kingii, Ceriodaphnia cornuta,
Moina macrocopa, and Daphnia similoides to the copepod Mes. pehpeiensis. Two experiments
were conducted: (a) life table demographics in a control and in water
preconditioned by the copepod, and (b) population dynamics in a
control, in the presence of the copepod, and in water preconditioned by
the copepod. With the exception of S. kingii, average reproductive
rates in the other 3 cladocerans were significantly higher in
copepod-conditioned water than in the control. Furthermore, D. similoides showed a higher
increase in reproductive rates in copepod-conditioned water than did
the other 3 cladoceran species. The presence of the copepod
severely suppressed the population growth trajectories of all 4
cladoceran species tested. The copepod-imposed reduction in
population growth rates was significantly higher for Moi. macrocopa and S. kingii. With the exception
of S. kingii, the other 3
cladocerans reproduced earlier in the copepod treatment. The
neonate size at hatching and maximum body sizes reached by the 3
cladocerans (except S. kingii)
in treatments were larger than those in the controls.
Key words: Cyclopoida,
Predation, Cladocera, Conditioned water, Life table.
*Correspondence: E-mail:Jshwang@mail.ntou.edu.tw
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