47 research outputs found
Polyunsaturated fatty acids in fishes increase with total lipids irrespective of feeding sources and trophic position
Trophic transfer and retention of dietary compounds are vital for somatic development, reproduction, and survival of aquatic consumers. In this field study, stable carbon and nitrogen isotopes, and fatty acids (FA) contents in invertebrates and fishes of pre-alpine Lake Lunz, Austria, were used to (1) identify the resource use and trophic level of Arctic charr (Salvelinus alpinus), pike (Esox lucius), perch (Perca fluviatilis), brown trout (Salmo trutta), roach (Rutilus rutilus), and minnow (Phoxinus phoxinus) and (2) examine how polyunsaturated fatty acids (PUFA; i.e., omega-3 and -6 PUFA) are related to total lipid status, littoral-pelagic reliance, and trophic position. Stable isotope data suggest that pike, perch, and minnow derived most of their energy from littoral resources, but minnows differed from pike and perch in their trophic position and PUFA composition. The co-occurrence of cyprinids, percids, and pike segregated these fishes into more lipid-rich (roach, minnow) and lipid-poor (pike, percids) species. Although the relatively lipid-poor pike and percids occupied a higher trophic position than cyprinids, there was a concurrent, total lipid-dependent decline in omega-3 and -6 PUFA in these predatory fishes. Results of this lake food-web study demonstrated that total lipids in fish community, littoral-pelagic reliance, and trophic position explained omega-3 and -6 PUFA in dorsal muscle tissues. Omega-3 and -6 PUFA in these fishes decreased with increasing trophic position, demonstrating that these essential FAs did not biomagnify with increasing trophic level. Finally, this lake food-web study provides evidence of fish community-level relationship between total lipid status and PUFA or stable isotope ratios, whereas the strength of such relationships was less strong at the species level.Peer reviewe
On realcompact topological vector spaces
[EN] This survey paper collects some of older and quite new concepts and results from descriptive set topology applied to study certain infinite-dimensional topological vector spaces appearing in Functional Analysis, including Frechet spaces, (L F)-spaces, and their duals, (D F)-spaces and spaces of continuous real-valued functions C(X) on a completely regular Hausdorff space X. Especially (L F)-spaces and their duals arise in many fields of Functional Analysis and its applications, for example in Distributions Theory, Differential Equations and Complex Analysis. The concept of a realcompact topological space, although originally introduced and studied in General Topology, has been also studied because of very concrete applications in Linear Functional Analysis.The research for the first named author was (partially) supported by Ministry of Science and Higher Education, Poland, Grant no. 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