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An insertion (In)/deletion (Del) polymorphism in the fatty acid desaturase 2 (FADS2) gene, which codes for D6-desaturase, was for the first time observed in fish. The polymorphism is located in the seventh intron of FADS2 and the insertion consists of eleven repeats of CTGT (44 bp) with an allelic frequency, for the insertion, of 39 %. The polymorphism was associated with a modulation in D6-desaturase activity as significant effects on the ratio of EPA or DHA to their precursors were found (P,0·001). A different distribution of SFA, MUFA and PUFA among the In/In, In/Del and Del/Del groups was also detected in fish fillet. The results suggest that genetic selection for this marker might improve the ability of European grayling to utilise dietary n-3 long-chain PUFA precursors, as D6-desaturase is the rate-limiting enzyme in the production of EPA and DHA from a-linolenic acid.Key words: D6-Desaturase: EPA: DHA: Thymallidae: Mutations: Fish Fish have the ability to elongate and/or desaturate fatty acid precursors to synthesise long-chain (LC) PUFA (1) , but the efficiency of this metabolic pathway varies among fish species. In contrast to marine finfish species where the ability of synthesising LC-PUFA from precursors is limited and controversial (2,3) , freshwater fish seem to be able to maintain a certain degree of D6-, D5-desaturase and elongase activities to produce arachidonic acid, EPA and DHA if their precursors linoleic and a-linolenic acids (ALA) are present in their diet. Fatty acid desaturase 2 (FADS2), also called D6-desaturase, is the rate-limiting enzyme in the production of EPA and DHA from ALA (4) even if two other enzymes (FADS1/D5-desaturase and elongase) are involved in this biosynthetic pathway.

Workflow integration is a problem common to many organizations, that need to develop and run applications composed by multiple related tasks, possibly heterogeneous and performed on or by heterogeneous processing entities. Often some of the systems to be integrated have a very large autonomy, and concede only very limited visibility of their internal organization. The limit case is given by legacy applications, i.e. old, typically mainframe based applications designed with little or no interface with other applications. In this paper we discuss the design and the implementation of a prototype system for development and the management of such distributed workflow applications. To carry out the integration process we propose both a graphical formalism to represent the access procedure to legacy host, and global application that involve the access of several host. This formalism allows to represent such concurrent processing application in a totally structured way, and includes provisions to represent different kind of parallel processing, and the handling of asynchronous exceptions.