Seasonal variations in fatty acid composition in several tissues of a 1-year-old population of giant lion's-paw scallop Nodipecten subnodosus were analyzed during gonad development. Samples were taken bimonthly from December 1999 to June 2000, a period in which gonad development was occurring. Fatty acid accumulation in neutral and polar lipids of the female gonad was concomitant to the gonad development and presented a maximum in June. Among essential fatty acids, a specific accumulation was observed only for 20:5n - 3 in the female gonad, as suggested by an increase in its proportion in the neutral and the polar fractions. However, no specific accumulation was observed for 22:6n - 3, as its proportion remained relatively constant in both fractions. We suggest that a specific increase of 22:6n - 3 is not necessary during gametogenesis because its proportion was high enough for reproductive purposes (20-30%). Although some data suggest a partial mobilization of polyunsaturated fatty acids from the muscle and digestive gland to the female gonad during gonad development, the main supply came directly from the diet. The maximum increase in total and specific fatty acids in the digestive gland occurred in April and was maintained in June. These changes reflect either a higher lipid availability of the food, or the beginning of storage process in the digestive gland. However, in the female gonad, the maximum increase was observed in June, whereas gonad development and spawning were observed from April. It is suggested that different patterns of lipid accumulation in the first (April) and second (June) maturation processes could be related to the reproductive cycle of this species, which exhibits an initial facultative maturation during spring and the main reproductive activity during summer. © 2005 Elsevier B.V. All rights reserved.