Marine Biology Research Division

This is the first of a series of publications planned as guides to aquatic Heteroptera of Singapore and Peninsular Malaysia to be published in the Raffles Bulletin of Zoology. A key to families and a list of known genera with number of described species for each genus are given.

Seven species of sea-skaters, marine insects of the genus Halobates, are reported from Micronesia. Nymphs of nearshore species (H. mariannarum, H. flaviventris, H. nereis, H. princeps) are generally found in sheltered waters among mangrove roots and branches, whereas adults are usually found in more open water. Specimens of open-ocean species (H. micans, H. sericeus, H. germanus) may be found washed to shore after storms. Under laboratory conditions, each nymphal stadium of H. mariannarum lasts 12- 14 days.

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 74-92s of the total lipid, while in Rheumatobates and Gerris it is only 46-720/O.  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.