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Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development of Chironomus riparius

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Abstract:

We quantified somatic growth, development, and emergence of the midge Chironomus riparius on experimental diets (oats, Spirulina, and Tetraphyll®) covering gradients in food quality (differing polyunsaturated fatty acids) and quantity (0.1–5.4 mg C·day–1). Additionally, similar incubations without food additions were made using a food-poor sediment containing peat and the green alga Scenedesmus obliquus. Larval and adult size was affected by both food quantity and quality and increased some three to four times across the food concentration gradients. Adult emergence, however, was affected only by food quantity. A type 3 response model showed that a saturation level was reached for the oats treatment at 2.7 mg C·day–1 (or 3.9 µg 3 and 120 µg 6 polyunsaturated fatty acids·day–1), indicating that the quality of oats constrained further stimulation of larval growth. In the peat treatment, larval growth was very low, no adults emerged, and no larvae even made it to the pupa stage. Fatty acid analyses showed that larvae were capable of synthesizing arachidonic acid via -linolenic acid by Δ6- and Δ5-desaturase activity using linoleic acid available in food sources. This strongly suggests that C. riparius is not dependent on dietary sources of eicosapentaenoic acid and arachidonic acid and can sustain viable populations even under a low-quality food regimen.

Nous avons mesuré quantitativement la croissance somatique, le développement et l'émergence chez des moucherons Chironomus riparius nourris de régimes expérimentaux (avoine, Spirulina et Tetraphyll®) qui représentent des gradients de qualité (différences d'acides gras polyinsaturés) et de quantité (0,1–5,4 mg C·jour–1) de nourriture. Nous avons, de plus, fait des incubations semblables sans ajout de nourriture sur un sédiment pauvre en nourriture et contenant de la tourbe et l'algue verte Scenedesmus obliquus. La taille des larves et des adultes est affectée tant par la quantité que la qualité de la nourriture et elle augmente par un facteur d'environ 3–4 sur les gradients de concentration de nourriture. L'émergence des adultes, cependant, n'est affectée que par la quantité de nourriture. Un modèle de réponse de type 3 montre que le niveau de saturation dans le cas du régime d'avoine est atteint à 2,7 mg C·jour–1 (ou 3,9 µg 3 et 120 µg 6 acides gras polyinsaturés·jour–1), ce qui indique que la qualité de l'avoine restreint toute stimulation subséquente de la croissance larvaire. Dans les conditions expérimentales avec de la tourbe, la croissance larvaire est très basse, aucun adulte n'émerge et même aucune larve n'atteint le stade nymphal. Des analyses des acides gras montrent que les larves sont capables de synthétiser l'acide arachidonique en passant par l'acide -linoléique par l'activité des désaturases Δ6 et Δ5 en utilisant l'acide linoléique présent dans les sources alimentaires. Ces résultats indiquent nettement que C. riparius ne dépend pas de sources alimentaires d'acide eicosapentaénoïque et d'acide arachidonique et qu'il peut maintenir des populations viables même avec un régime alimentaire de faible qualité.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: March 1, 2007

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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