Differential response of lipid metabolism and membrane physical state by an actively and passively overwintering planktonic crustacean

Abstract

Phospholipid (PL) composition, fatty acid (FA) composition of total and major individual PL as well as the physical state of isolated PL were investigated in relation to temperature exposure by freshwater planktonic crustaceans,Cyclops vicinus andDaphnia magna. C. vicinus, adapted to warm water, accumulated appreciable amounts of docosahexaenoic acid in its PL within 3 days when the temperature was decreased from 20 C to 10 C. Docosahexaenoic acid was preferentially esterified to phosphatidylethanolamine (PE). Docosapolyenoic FA were absent in PL ofD. magna and this species did not increase polyenoic acid level under identical temperature treatment. The level of PE was elevated, however, in both species in response to decreased environmental temperature. Two characteristic breaks were observed in ln S vs 1/T plots of 5‐doxyl stearic acid spin probs. These were at 19 C and 13 C forC. vicinus and at 20 C and 7 C forD. magna. C. vicinus shifted both the upper and lower phase‐separation temperatures of its PL to lower temperatures when exposed to cold. Differences between the onset and completion of phase‐separation temperatures equalled that in environmental temperature (10 C). The phase‐separation temperatures ofD. magna were unchanged under identical experimental conditions. Results are interpreted as a complete temperature adaptation of membrane transitional state byC. vicinus but not byD. magna. Researchers have postulated that one of the reasons the latter species cannot overwinter in an active form as doesC. vicinus, but instead overwinters as resting eggs, involves its failure to adapt membrane PL composition and physical state to temperature.

Combined effects of food quality and temperature on somatic growth and reproduction of two freshwater cladocerans

“…In addition, Schlechtriem et al (2006) found that retention of EPA by daphnids was clearly influenced by temperature because significantly higher levels of EPA were found in individuals reared at 11uC compared with those kept at 22uC, suggesting that EPA requirements of cladocerans increase with decreasing temperature. Farkas (1984) argued that the ability of zooplanktonic species to adapt their membranes at low temperature depends on their ability to incorporate PUFA. More generally, the level of unsaturation of fatty acids of poikilotherms increases at low temperature in membrane lipids, lending support to Schlechtriem's and Farkas's results (Nishida and Murata 1996).…”

“…In nature, cladocerans have thus to optimize their fitness with a trade-off between temperature and food availability. Earlier work from Farkas et al (1984) investigated the effect of temperature on zooplankton's ability to adapt their cell membrane lipid composition. Unlike the complete fatty acid adaptation in membranes of Cyclops vicinus to changing temperature, Farkas et al (1984) argued that Daphnia magna fails to incorporate PUFA into phospholipids at lower temperatures and suggested that failure to overwinter in an active state is related to their ability to adapt the lipid composition of their cell membranes to lower (winter) temperatures.…”

“…Earlier work from Farkas et al (1984) investigated the effect of temperature on zooplankton's ability to adapt their cell membrane lipid composition. Unlike the complete fatty acid adaptation in membranes of Cyclops vicinus to changing temperature, Farkas et al (1984) argued that Daphnia magna fails to incorporate PUFA into phospholipids at lower temperatures and suggested that failure to overwinter in an active state is related to their ability to adapt the lipid composition of their cell membranes to lower (winter) temperatures. However, although the tradeoff between food quantity and water temperature for maximizing fitness of the key herbivore Daphnia has been the subject of several studies (Dawidovicz and Loose 1992;Mitchell 1997;Lampert et al 2003), the interaction between food quality and temperature remains still poorly understood.…”

Interaction of changes in food quality and temperature reveals maternal effects on fitness parameters of a keystone aquatic herbivore

“…Dietary deficiency in EPA content has been shown to have greater effect on zooplankton growth and reproduction at lower temperatures (Masclaux et al 2009). PUFAs, such as EPA, are important for maintaining membrane fluidity of ectotherms at low temperatures, and some aquatic ectotherms are capable of increasing the PUFA content of their lipid membranes in response to cold (Farkas et al 1984). However, Daphnia have shown low rates of conversion of C18-PUFA into EPA (Farkas et al 1984;Weers et al 1997), and their fatty acid composition largely resembles that of their diet (Weers et al 1997).…”

“…PUFAs, such as EPA, are important for maintaining membrane fluidity of ectotherms at low temperatures, and some aquatic ectotherms are capable of increasing the PUFA content of their lipid membranes in response to cold (Farkas et al 1984). However, Daphnia have shown low rates of conversion of C18-PUFA into EPA (Farkas et al 1984;Weers et al 1997), and their fatty acid composition largely resembles that of their diet (Weers et al 1997). Therefore Masclaux et al (2009) suggested that a higher dietary supply of EPA might be required at low temperatures.…”