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Fractionation and metabolic turnover of carbon and nitrogen stable isotopes in black fly larvae
Author(s) -
Overmyer Jay P.,
MacNeil M. Aaron,
Fisk Aaron T.
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3413
Subject(s) - fractionation , chemistry , isotopes of nitrogen , isotopic signature , larva , δ13c , nitrogen , black fly , isotope fractionation , δ15n , zoology , turnover , stable isotope ratio , metabolism , feces , environmental chemistry , biology , biochemistry , chromatography , ecology , physics , organic chemistry , management , quantum mechanics , economics
Diet‐tissue fractionation factors and metabolic turnover rates of δ 15 N and δ 13 C were assessed in laboratory‐reared black fly ( Simulium vittatum IS‐7) larvae fed isotopically distinct diets. Five treatments consisted of using food with different δ 15 N signatures throughout the experiments (19–26 days), a sixth shifted from a low to high δ 15 N signature diet ( uptake ) on day 14, and the last shifted from a high to low δ 15 N signature diet ( elimination ) on day 14. In the larvae, diet‐tissue fractionation factors for δ 13 C, which were in steady state with food, ranged from −0.61 to 2.0, with a median of 1.87. The δ 15 N diet‐tissue fractionation factors were mostly negative, ranging from +2.85 to −24.96‰, with a single positive value from the elimination treatment in which larval δ 15 N did not achieve steady state with the food. Diet‐tissue fractionation factors also had a significant negative relationship (r 2 = 0.98) with δ 15 N values in the food suggesting that nitrogen diet‐tissue fractionation factors are 15 N concentration‐dependent. The δ 15 N of shed head capsules and feces were enriched in 15 N and could be mechanisms for elimination of 15 N by the larvae. For δ 15 N, metabolic turnover values based on the Hesslein model were highly consistent (0.40 to 0.43 δ 15 N*day −1 ) between uptake and elimination phases and across experiments and were an order of magnitude greater than growth rates. The rapid turnover of nitrogen in black fly larvae, which was orders of magnitude greater than measured in vertebrates, makes them an excellent indicator of short‐term changes in nitrogen inputs to aquatic systems. Copyright © 2008 John Wiley & Sons, Ltd.