Seasonal changes in the phospholipid composition in thoracic muscles of a heteropteran, Pyrrhocoris apterus

The fatty acid composition of phospholipids in thoracic muscles of Pyrrhoco ris apterus was related to acclimatization temperature and diapause. Two un saturated fatty acids, linoleic (18:2n-6) and oleic (18:1n-9), and two satu rated, palmitic (16:0) and stearic (18:0), dominated at all temperatures. I n contrast to most other reports, the proportion of unsaturated fatty acids did not increase with decreasing temperature; there was a positive correla tion between the unsaturation ratio and temperature in total phospholipids (r=0.67). The most prominent response to cold acclimatization was an increa se in the proportion of 16:0 fatty acid and a corresponding decrease in the proportion of fatty acids with 18 carbons. The negative correlation betwee n the proportion of 16:0 and temperature was stronger in phospholipids with phosphatidylethanolamine (PE) head group (r=-0.85) than in phospholipids w ith phosphatidylcholine (PC) head group (r=-0.58). Changes in fatty acid pr ofiles associated with photoperiodic induction of diapause had the same tre nd as changes related to cold acclimatization. Similar to most other report s, the proportion of PE increased, while the proportion of PC decreased wit h decreasing temperature. In contrast to a general rule, the PE-phospholipi ds were less unsaturated than PC-phospholipids. (C) 1999 Elsevier Science L td. All rights reserved.