Limnocalanus macrurus is an important memberof the zooplankton communities of the Siberian shelfseas. During the cruise, Boris Petrov 1999, in August/September to the southern Kara Sea and the Ob andYenisej estuaries, its abundance and vertical distributionwere investigated. In adults, salinity tolerance, egg production,feeding and lipid composition were studied.L. macrurus occurred in water with salinities rangingfrom 1.7 to >33 without clear preference, as revealedfrom salinity-tolerance experiments. The dominance ofadults and their high wax-ester content, as well as thelack of egg production and feeding activity, suggest thatthe population was in the pre-overwintering condition.Wax esters allow L. macrurus to survive long starvationperiods and to reproduce in times of little food availability,but through its potential carnivory, it should beable to replenish its diet by preying on other zooplankton.Morphology and swimming behaviour of L. macrurusresemble the omnivorous copepod Metridialonga, which, however, is mainly found in the openocean. The overall lipid composition and the mode oflipid storage also point to an omnivorous feedingbehaviour. However, the high proportion of the markerfatty acid 16:1(n-7) suggests that L. macrurus stronglyexploited the existent phytoplankton bloom, consistingmainly of diatoms. A striking characteristic of its lipidsis the high level of the 20:1(n-7) fatty alcohol in additionto the 18:1(n-7) fatty acid and alcohol. It is the firstcopepod species known to produce such high amountsof 20:1(n-7) alcohol. Since this alcohol and the correspondingfatty acid are not abundant in any prey, thislong-chain monounsaturated wax-ester moiety has to beproduced de novo. Owing to these particular lipidcharacteristics in its distribution, feeding, and life-cyclestrategy, L. macrurus can be described as a very versatileand opportunistic copepod.