[Combined effect of environmental temperature and trematodes on fatty acids composition of lipids of Littorina saxatilis (Olivi 1792) (Gastropoda, Prosobranchia)].

An effect of environmental temperatures and invasion by helminthes larvae on fatty acids composition of digestive gland lipids of marine littoral gastropod Littorina saxatilis from White Sea and Barents Sea was investigated. We have compared gastropods from boreal and subarctic populations. It was found that gastropods from waters of lower temperature have increased omega3/omega6 fatty acids ratio. However, saturation index of individual membrane phospholipids was not affected. Also, content of eicosenoic acid (20:1) in individual phospholipids was not affected by temperature. Invasion increases the omega3/omega6 ratio of common lipids but not the omega3/omega6 ratio of common and individual phospholipids with the exception of phosphatidilcholine of cold water mollusks from Barents Sea that had this ratio doubled. In contrast to temperature, invasion affects the content of eicosenoic acid that was increased in the investigated organs. Adaptability of these effects is discussed regarding parasite-host system.