Tiphaine Labed-Veydert, A. Bec, M. Danger, F. Perrière, C. Desvilettes
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引用次数: 0
Abstract
ABSTRACT Headwater streams are characterised by predominantly heterotrophic functioning resulting from leaf litter input, but autochthonous primary production can also contribute to energy fluxes and the supply of nutrients. While much work has focused on the role of polyunsaturated fatty acids as essential nutrients, less attention has been paid to the significance of sterols in stream food webs. Yet these molecules are essential to arthropods that can only synthesise cholesterol from a limited range of dietary sterols. In a headwater stream, we tracked the transfer of dominant sterols from allochthonous and autochthonous resources to 5 benthic macroinvertebrates. Despite their formal functional feeding group, all the taxa tended to be opportunistic omnivores that relied on all available resources. These behaviours could be attributed to nutritional constraints in the stream food web, but these constraints were not related to the sterol supply from the different basal sources. Dominant sterols from detrital sources (leaf litter, fine benthic organic matter [FBOM]) and primary producers (epilithic biofilms, bryophytes) were all Δ5-sterols (β-sitosterol, campesterol, stigmasterol, epibrassicasterol). The levels of cholesterol detected in macroinvertebrates, as well as the presence of desmosterol, indicate efficient dealkylation activity of these Δ5-sterols. Leaf litter has consistently shown high β-sitosterol/stigmasterol ratios, giving it greater nutritional value than usually accepted. But bryophytes, and especially epilithic biofilms, contained cholesterol, providing a direct supply to invertebrates, thereby promoting their growth. Detrital particles (FBOM) colonised by microalgae could be the best-balanced diet to avoid sterol deficiencies due to their cholesterol content and high β-sitosterol/stigmasterol ratios.
期刊介绍:
Inland Waters is the peer-reviewed, scholarly outlet for original papers that advance science within the framework of the International Society of Limnology (SIL). The journal promotes understanding of inland aquatic ecosystems and their management. Subject matter parallels the content of SIL Congresses, and submissions based on presentations are encouraged.
All aspects of physical, chemical, and biological limnology are appropriate, as are papers on applied and regional limnology. The journal also aims to publish articles resulting from plenary lectures presented at SIL Congresses and occasional synthesis articles, as well as issues dedicated to a particular theme, specific water body, or aquatic ecosystem in a geographical area. Publication in the journal is not restricted to SIL members.