caa a22 4500 445894792 CHVBK 20180317145628.0 cr unu---uuuuu 170323e20110601xx s 000 0 eng 10.1007/s10750-010-0534-y doi (NATIONALLICENCE)springer-10.1007/s10750-010-0534-y Identification of the critical timing of sex determination in Daphnia magna (Crustacea, Branchiopoda) for use in toxicological studies [Elektronische Daten] [Danielle Ignace, Stanley Dodson, Donna Kashian] Daphnia are often used as test organisms to determine toxicity of chemicals found in the environment. Fecundity and mortality are the classic endpoints in such tests; however, there is increased interest in other sub-lethal endpoints. Most Daphnia reproduce by cyclic parthenogenesis, typically reproducing asexually to produce genetically identical females. Environmental cues trigger the production of males allowing for sexual reproduction. This ability to switch reproductive strategies has been increasingly used as a bioassay endpoint in screens for sub-lethal effects of contaminants. In order to optimize such test, it is necessary to know when sex is determined during Daphnia development. A previous study using the insect juvenile hormone methyl farnesoate has shown that sex determination occurred during the egg maturation period in Daphnia. Our study exposed female Daphnia magna carrying eggs and embryos at different stages of maturation, to the insecticide toxaphene to determine if the timing of sex determination is similarly influenced by a pesticide. Our results suggest that in response to toxaphene exposure sex is determined in the immature oocyte, before the final maturation cleavage, and before the developing egg is extruded into the brood chamber. Thus, sex determination is transgenerational, being determined while the egg is still immature and in the mother's ovary. Springer Science+Business Media B.V., 2010 Sex determination nationallicence Toxaphene nationallicence Daphnia nationallicence Ignace Danielle Department of Ecology & Evolutionary Biology, The University of Arizona, BioSciences West room 310, 1041 E. Lowell St., 85721, Tucson, AZ, USA aut Dodson Stanley Department of Zoology, University of Wisconsin, Birge Hall, 430 Lincoln Drive, 53706-1381, Madison, WI, USA aut Kashian Donna Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Rm. 3115, 48202, Detroit, MI, USA aut Hydrobiologia Springer Netherlands 668/1(2011-06-01), 117-123 0018-8158 668:1<117 2011 668 10750 https://doi.org/10.1007/s10750-010-0534-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10750-010-0534-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ignace Danielle Department of Ecology & Evolutionary Biology, The University of Arizona, BioSciences West room 310, 1041 E. Lowell St., 85721, Tucson, AZ, USA aut NATIONALLICENCE 700 1- Dodson Stanley Department of Zoology, University of Wisconsin, Birge Hall, 430 Lincoln Drive, 53706-1381, Madison, WI, USA aut NATIONALLICENCE 700 1- Kashian Donna Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Rm. 3115, 48202, Detroit, MI, USA aut NATIONALLICENCE 773 0- Hydrobiologia Springer Netherlands 668/1(2011-06-01), 117-123 0018-8158 668:1<117 2011 668 10750 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer