water Article MAPKs and HSPs’ Activation of a Natural Daphnia magna Population in a Man-Perturbed Lake: Implications of Ecological Significance Maria Demertzioglou 1,2, Efthimia Antonopoulou 1 , Dimitra Voutsa 3, Argyri Kozari 3, Maria Moustaka-Gouni 2 and Evangelia Michaloudi 1,* 1 Department of Zoology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;
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[email protected] (A.K.) * Correspondence:
[email protected]; Tel.: +30-2310-998-265 Abstract: Natural and anthropogenic pressures in inland waters induce molecular response mecha- nisms in organisms as a defense against such multiple stressors. We studied, for the first time, the expression of the stress proteins, heat shock proteins (HSP) and mitogen-activated proteins kinase (MAPK), in a Daphnia magna natural population as a response to environmental changes in a heavily modified water body (Lake Koronia, Northern Greece). In parallel, the water physicochemical parameters, nutrients’ concentration and phytoplankton abundance were measured. Our results showed fluctuations of the proteins’ levels (HSP70, HSP90, phospho-p38 MAPK, phospho-p44/42 MAPK) providing evidence of their expression in situ. HSP70 showed an increasing tendency while Citation: Demertzioglou, M.; for HSP90, no tendency was recorded. The MAPKs’ members followed a reverse pattern compared Antonopoulou, E.; Voutsa, D.; Kozari, A.; Moustaka-Gouni, M.; Michaloudi, to each other.