Author/Editor		Simčič, Tatjana; Brancelj, Anton
Title		Respiratory electron transport system (ETS) activity as an estimator of the thermal tolerance of two Daphnia hybrids
Type		članek
Source		J Plankton Res
Vol. and No.		Letnik 26, št. 5
Publication year		2004
Volume		str. 525-34
Language		eng
Abstract		The influence of temperature on the activity of the respiratory electron transport system (ETS) was measured in one clone of Daphnia hyalina x galeata and one of Daphnia cucullata x galeata, isolated from Lake Bled (Slovenia). The ETS activity of ovigerous females acclimated to 7,20 and 25degrees C, was measured at 5, I0, 15, 20, 25 and 30degrees C. Population growth experiments showed that D. cucullata x galeata grew better at high rather than low temperatures. Daphnia hyalina x galeata, however, grew more succesfully at low temperatures than did D. cucullata x galeata. The highest Ql0 of ETS activity of D. cucullata x galeata at the lowest temperature range of 5-15degrees C indicated the absence of enzymes that could function sufficiently well at lowe temperatures. The ETS activity of the warmacclimated hybrid D. hyalina x galeata reached a maximum at an incubation temperature of 20degrees C, while D. cucullata x galeata had maximal ETS activity at 25degrees C. Thus D. cucullata x galeata has a more efficient enzyme system than D. hyalina x galeata at the higher temperature. The higherArrhenius activation energy (Ea) for D. cucullata x galeata than for D. hyalina x galeata indicates that enzymes from D. cucullata x galeata are more temperature sensitive than those from D. hyalina x galeata. In conclusion, the ETS of D. cucullata x galeata is adapted to a higher temperature and to narrower temperature fluctuations than that of D. hyalina x galeata.
Descriptors		ELECTRON TRANSPORT TEMPERATURE DAPHNIA POPULATION GROWTH HYBRIDIZATION