A comparative study of the lipids of water‐striders from marine, estuarine, and freshwater environments: Halobates, Rheumatobates, Gerris (Heteroptera: Gerridae)1

The lipids of water‐striders from three different aquatic environments (marine‐Halobates germanus and Halobates sericeus; estuarine‐Rheumatobates aestuarius; and freshwater‐ Gerris remigis) differ considerably in their fatty acid composition. The polyunsaturated 22 : 6 fatty acid, present only in Halobates, is presumably derived from its marine plankton food. The 20 : 5 acid is a major component of the lipids of Gerris and Rheumatobates, which feed on terrestrial insects known generally to lack long‐chain (> C‐18) polyunsaturated acids; it is presumably synthesized by chain elongation from C‐18 precursors. Differences in food and habitat may account for some of the observed differences in fatty acid composition. Neutral triglyceride lipids are stored in all three genera: in Halobates this fraction represents 74−92% of the total lipid, while in Rheumatobates and Gerris it is only 46–72%. The triglycerides are rapidly utilized during starvation by Halobates and Rheumatobates. Pristane, the major hydrocarbon of many marine zooplankton, is apparently absent from the lipids of Halobates.