Biochemical Systematics and Ecology, Vol. 17, No. 7/8, pp. 583-587, 1989. Printed in Great Britain, 0305-1978/89 $3.00 + 0.00 O 1989 Pergamon Press plc. Lipid Composition and Storage balthica the Tissues of the Blvalve, Macoma R. WENNE* and L. POLAKt * lnstitute of oceanology, Polish Academy of Sciences, PowstańcóW Warszawy 55, 81-967 Sopot, Poland; tSea Fisheries lnstitute, Al Z,iednoczenia 1, 81-345 Gdynia, Poland r.ey Word lndex-Macoma balthica; lipids; fatty acids, Abstract-Total lipid content, lipid classes and fatty acid composition in organs ol Macoma balthica | L) from the Gulf of Gdańsk (Puck Bay) were studied in different seasons. Marked differences among tissues in lipid class composition were observed, Triacylglycerides were accumulated in the hepatopancreas and in the female gonad in large quantities, while hydro- carbons were concentrated in male gonads, gills, muscles and mantle. Fatty acid composition of gill lipids reflects the brack- ish water conditions of the Gulf of Gdańsk in which Macoma balthica occurs. in lntroduction Contrary to most other bivalve species, in Macoma balthicafrom the Baltic Sea, lipids have been reported to be the most important energy storage substances |1, 2]. Total lipid content in the tissue dry weight of the clam has been reported to exceed 22% 13, 4], or even 35% [5], and this is responsible for the exceptionally high energetic values of the body t6]. lt has been concluded that triacylglycerides are the main lipid class involved in energy storage 17, 8]. Total Iipid was mainly stored in M. balthica hepatopancreas and gonads [9, 10]. However, Iipid c|ass and fatty acid distribution and storage in different organs of this clam had not been investigated. ln this paper we report changes in the lipid classes and fatty acid composltion in different tissues and discuss Iipid storage in a brackish water clam, M. balthica, in comparison with those in typically marine as wel| as in fresh-water bivalve species. Results Values of the morphometric condition index CĄ: body dry weight X 1000/shell weight obserued in summer 1985 were approximately 200 and Clr: body dry weight (mg) X 1000/shell (Received 27 Jtne 1989) length3 (mm') were 10.99-11.58. Body dry weight of standard M. balthica with shell length 17 mm was below 60 mg throughout 1985 and was lowest in the winter of 1986. The hepatopancreas comprised approxi- mately 50% of M. balthica body dry weight, mant|e 12oń, food 5oń, adductor 2-3Yo, gills 2-5% and gonad up to 8%. The hepatopancreas contained from 75% (in winter) to 85% (in spring-summer) of the whole lipid resources in the body. Ripe gonads contained up to 15% of lipids. Tota! lipid content and lipid classes compo- sition in particular organs and whole specimens of M. balthica from the Gulf of Gdańsk is shown in Table 1. The highest Iipid content in tissue dry weight was found in the hepatopancreas and gonads, whereas the lowest was in the mantle and muscles. The hepatopancreas in animals collected from deep parts of the GuIf of Gdańsk (75 m) contained even more lipids (up to U% dry wt). No seasonal changes in totaI lipid content were obserued in whole animals or in organs. A predominant component of liplds (over 60%| in the hepatopancreas and female gonad are triacylglycerides. Their content in the male gonad is about half of that in the female organ. Significant seasonal changes in triacyl- glyceride content in lipids were obserued in the mantle; its values were lowest in winter. Considerable content of hydrocarbons was