Impacts of multistressors on the survival and life history traits of Daphnia Pulex

Bezirci, Gizem
As Daphnia have an important role in freshwater food webs, it is important to understand how environmental stressors affect their survival and life history traits. Daphnia pulex were first acutely exposed to a combination of NaCl salinities (0.00-10.0 g/L) and fish-exuded kairomone. The 24 and 48 hour LC50 values were 0.401 and 0.159 g/L in kairomone-absence and 1.962 and 1.007 g/L in kairomone-presence. Hence, survival decreased with increasing salinity, while the kairomone enhanced daphnid resistance to salinity below 2 g/L. During the chronic exposure to salinity (0.00-1.5 g/L) combined with the fish-exuded kairomone, impacts of temperature and food were also investigated. Survival decreased significantly with increased salinity, while the kairomone had a positive impact on survival at intermediate salinity levels, suggesting an antagonistic relationship. Temperature alone had a significant negative impact on survival and its combined effect with salinity and fish kairomone was synergistic. However, the impact of food limitation was insignificant. Life history parameters were affected by both salinity and the fish-exuded kairomone, the combination of which significantly decreased the body length: width ratio. Egg number/individual decreased with salinity and increased in the presence of the fish kairomone. In conclusion, the combined impact of salinity and fish-exuded kairomone significantly affected daphnid survival and life history traits in a non-linear manner, such that fish kairomone enhanced daphnid resistance to intermediate salinity levels. Moreover, the combined effect of salinity, temperature and fish kairomone on daphnid survival was also significant.


Effect of drought and salt stresses on the gene expression levels of antioxidant enzymes in lentil (lens culinaris m.) seedlings
Aksoy, Emre; Yücel, Ayşe Meral; Department of Biology (2008)
This study was carried out for understanding of antioxidant mechanisms of lentil under abiotic stress conditions. For this aim, 14 days old lentil seedlings (Lens culinaris Medik cv. Sultan-1) were subjected to drought (20% PEG 6000), and salt (150 mM NaCl ) stress for 6, 12 and 24 hours, for 3, 5 and 7 days. PCR conditions for Mn SOD, Cu/Zn SOD, chloroplastic/mitochondrial GR, CAT and chloroplast /stromal APX antioxidant enzymes were optimized. Then, total RNA was isolated from stressed and non-stressed pl...
Role of hydrology, nutrients and fish predation in determining the ecology of a system of shallow lakes
Özen, Arda; Beklioğlu, Meryem; Department of Biology (2006)
In this study, the hydrology and physical, chemical and biological variables of a shallow lake system including the Lakes Mogan and Eymir between 1997-2005 were evaluated. In Lake Eymir, a biomanipulation study was conducted between August, 1998 December, 1999. Upon biomanipulation, Lake Eymir shifted to clearwater state with submerged vegetation domination during 2000-2003. However, in 2004, the lake shifted back to algae-dominated turbid state since the buffer mechanisms provided by submerged plants were...
Detection of species boundaries in the Rana Ridibunda complex of Southwestern Turkey using mitochondrial ND3 marker
Akın, Çiğdem; Bilgin, Cemal Can; Department of Biology (2007)
Water frogs are one of the most interesting vertebrate groups, showing great diversity and complexity in their reproductive modes, ecology and evolutionary relationships, and with many cryptic species due to high morphological similarity. For many decades, a single species, Rana ridibunda, has been suggested to exist in Turkey. However, the application of new morphometric, molecular and bioacoustic techniques has recently revealed the occurrence of several distinct water frog taxa in Turkey. In this study, ...
Proton relay network in P450cam formed upon docking of putidaredoxin
Ugur, Ilke; Chandrasekhar, Prasanna (Wiley, 2020-04-01)
Cytochromes P450 are versatile heme-based enzymes responsible for vital life processes. Of these, P450cam (substrate camphor) has been most studied. Despite this, precise mechanisms of the key OO cleavage step remain partly elusive to date; effects observed in various enzyme mutants remain partly unexplained. We have carried out extended (to 1000 ns) MM-MD and follow-on quantum mechanics/molecular mechanics computations, both on the well-studied FeOO state and on Cpd(0) (compound 0). Our simulations include...
Characterisation of glutathione s-transferase activity in Turkish red pine (Pinus brutia ten) : variation in environmentally cold stressed seedlings
Boyoğlu, Seyhan; İşcan, Mesude; Department of Biochemistry (2004)
Plants can not escape from biotic and abiotic stress factors such as, extreme temperatures, high light intensity, drought, UV radiation, heavy metals, and pathogen attack. Plants have versatile defens systems against such stress conditions. In this study, the role of glutathione S-transferases (GSTs) in cold stress conditions were examined. Glutathione S-transferases are the enzymes that detoxify natural and exogenous toxic compounds by conjugation with glutathione. Glutathione, an endogenous tripeptide, is...
Citation Formats
G. Bezirci, “Impacts of multistressors on the survival and life history traits of Daphnia Pulex,” M.S. - Master of Science, Middle East Technical University, 2008.