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Indirect prey effects: Some morphological and life history responses of Daphnia pulex exposed to Notonecta undulata 1
Author(s) -
Dodson Stanley I.,
Havel John E.
Publication year - 1988
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1988.33.6.1274
Subject(s) - daphnia pulex , predation , biology , predator , pulex , daphnia , branchiopoda , ecology , zoology , intraguild predation , cladocera , zooplankton
Although protected by enclosures from direct contact, three clones of Daphnia pulex respond similarly to the presence of the predator Notonecta undulata by producing small eggs and offspring having a 3.7% reduction in growth per instar, compared to Daphnia grown in the absence of Notonecta. Primiparous adults were 15% shorter in the presence of Notonecta. Predator enclosure experiments showed that the decrease in prey body size was not due to direct size‐selective predation. Results of experiments in which water was pumped from predator cultures to D. pulex clone SBL cultures suggested that the signal is carried by water, possibly a water‐soluble chemical, produced by actively feeding Notonecta. This “prey response” to Notonecta includes a smaller adult and neonatal body size, a lower lipid index, a shorter developmental time from neonate to adult, and no change in the clutch size or the percent survival, compared to predator‐absent controls. Food level had a complex effect on prey response: at low food levels the prey response disappeared. These morphological and developmental prey responses suggest that previous field experiments of predation and competition may have been improperly designed, that the lipid index depends on the presence of a predator as well as food concentration, and that secondary productivity based on the Edmondson egg ratio technique may be underestimated in the presence of predators.