The influence of feeding, photoperiod and selected solvents on the reproductive strategies of the water flea, Daphnia magna |
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Authors: | Zhang L Baer K N |
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Institution: | College of Pharmacy and Health Sciences, Division of Toxicology, The University of Louisiana at Monroe, Monroe, LA 71209-0470, USA. |
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Abstract: | The influence of different feeding rates, reduced photoperiod and ethanol and acetone exposure on male production in Daphnia magna was investigated. Male production was observed under reduced photoperiod (8-h light:16-h dark) in all food levels. However, the sex ratio of daphnids fed 1x10(6) algae cells increased significantly from that of daphnids fed 15x10(6) algae cells (0.486+/-0.059 and 0.271+/-0.027, respectively). Under normal photoperiod (16-h light:8-h dark) and low food conditions (3.75x10(6) algae cells), a statistically significant increase in the sex ratio was observed in daphnids exposed to acetone at EPA acceptable solvent limits (0.1 ml/l). A shift back to parthenogenetic reproduction was observed in acetone-exposed daphnids at high food levels (15x10(6) algae cells). The results indicate that the reproductive strategies of females are influenced by phenological (i.e. reduced photoperiod), dietary and exogenous chemical cues. |
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