TY - JOUR
T1 - Daphnid morphology deters fish predators
AU - Kolar, Cynthia S.
AU - Wahl, David H.
N1 - Funding Information:
Acknowledgements We gratefully acknowledge J. Gramer, P. Hays, and J. Netto for assisting in conducting laboratory experiments and examining contents of fish stomachs. Field collections were obtained by J. Boase, K. Goodwin, M. Herbert, and B. Nerbonne. J. Alster of the University of Illinois provided statistical consulting. C. Cáceres, J. Dettmers, J. Goodrich, T. Smith, and the Aquatic Ecology Discussion Group at the Kaskaskia Biological Station provided thoughtful insight and helped to improve the manuscript. Partial funding for this study was provided by the Illinois Department of Natural Resources, Division of Natural Heritage, through project number 4120951 and coordinated by Carl Becker.
PY - 1998/10
Y1 - 1998/10
N2 - Spine and helmet production in zooplankton are thought to provide protection from invertebrate rather than vertebrate predators. We examined selectivity for Daphnia lumholtzi, a species that exhibits extreme cyclomorphosis with a large helmet and long tail spine (total length can exceed 5 mm), by juvenile bluegill (15-80 mm) in the laboratory and field. Bluegill consumed more D. pulex than D. lumholtzi when the species were presented alone. When the daphnids were offered together in equal numbers, bluegill selected against D. lumholtzi. Bluegill foraging behavior helped explain the observed nonrandom feeding. Bluegill capture efficiency foraging on D. pulex was high (85-100%) and handling times were low (usually too short to detect), whereas efficiencies were lower (40-96%) and handling times were longer (1-3 s) when foraging on D. lumholtzi, particularly for fish < 50 mm. As they gained experience, bluegill < 50 mm that oriented towards D. lumholtzi rejected them more often than striking. In addition, more D. lumholtzi were rejected and expelled than were D. pulex. From these experiments, we conclude that larger bluegill (> 50 mm) are able to forage more successfully on D. lumholtzi than smaller fish. Selectivity by bluegill collected from a reservoir infested with D. lumholtzi verified our laboratory conclusions. Smaller bluegill selected against D. lumholtzi, whereas it was a preferred diet item for bluegill > 50 mm. These results show that the morphology of D. lumholtzi interferes with predation by small planktivorous fish, posing foraging constraints for these fish more similar to those of piscivores, where handling time is important, than to those of planktivores, where prey density is of primary importance.
AB - Spine and helmet production in zooplankton are thought to provide protection from invertebrate rather than vertebrate predators. We examined selectivity for Daphnia lumholtzi, a species that exhibits extreme cyclomorphosis with a large helmet and long tail spine (total length can exceed 5 mm), by juvenile bluegill (15-80 mm) in the laboratory and field. Bluegill consumed more D. pulex than D. lumholtzi when the species were presented alone. When the daphnids were offered together in equal numbers, bluegill selected against D. lumholtzi. Bluegill foraging behavior helped explain the observed nonrandom feeding. Bluegill capture efficiency foraging on D. pulex was high (85-100%) and handling times were low (usually too short to detect), whereas efficiencies were lower (40-96%) and handling times were longer (1-3 s) when foraging on D. lumholtzi, particularly for fish < 50 mm. As they gained experience, bluegill < 50 mm that oriented towards D. lumholtzi rejected them more often than striking. In addition, more D. lumholtzi were rejected and expelled than were D. pulex. From these experiments, we conclude that larger bluegill (> 50 mm) are able to forage more successfully on D. lumholtzi than smaller fish. Selectivity by bluegill collected from a reservoir infested with D. lumholtzi verified our laboratory conclusions. Smaller bluegill selected against D. lumholtzi, whereas it was a preferred diet item for bluegill > 50 mm. These results show that the morphology of D. lumholtzi interferes with predation by small planktivorous fish, posing foraging constraints for these fish more similar to those of piscivores, where handling time is important, than to those of planktivores, where prey density is of primary importance.
KW - Daphnia lumholtzi
KW - Morphology
KW - Predation
KW - Predator avoidance
KW - Selectivity
UR - http://www.scopus.com/inward/record.url?scp=0031771546&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031771546&partnerID=8YFLogxK
U2 - 10.1007/s004420050621
DO - 10.1007/s004420050621
M3 - Article
AN - SCOPUS:0031771546
SN - 0029-8519
VL - 116
SP - 556
EP - 564
JO - Oecologia
JF - Oecologia
IS - 4
ER -