Diet-consumer nitrogen isotope fractionation for prolonged fasting arthropods

作者：Mizota Chitoshi^*; Yamanaka Toshiro

来源：Isotopes in Environmental and Health Studies, 2011, 47(4): 483-488.

DOI：10.1080/10256016.2011.624615

• arthropods
• consumer
• fasting
• isotope biochemistry
• isotope ecology
• nitrogen-15
• nitrogen recycling

Nitrogen acquisition for cellular metabolism during diapause is a primary concern for herbivorous arthropods. Analyses of naturally occurring stable isotopes of nitrogen help elucidate the mechanism. Relevant articles have cited (58 times up to mid-June 2011) anomalously elevated delta N-15(per mil deviation of N-15/N-14, relative to atmospheric nitrogen = 0 parts per thousand) values (diet-consumer nitrogen isotope fractionation; up to 12 parts per thousand) for a prolonged fasting raspberry beetle (Byturus tomentosus Degeer (Coleoptera: Byturidae)), which feeds on red raspberries (Rubus idaeus: delta N-15 = similar to + 2 parts per thousand). Biologists have hypothesised that extensive recycling of amino acid nitrogen is responsible for the prolonged fasting. Since this hypothesis was proposed in 1995, scientists have integrated biochemical and molecular knowledge to support the mechanism of prolonged diapausing of animals. To test the validity of the recycling hypothesis, we analysed tissue nitrogen isotope ratios for four Japanese arthropods: the shield bug Parastrachia japonensis Scott (Hemiptera: Cydnidae), the burrower bug Canthophorus niveimarginatus Scott (Hemiptera: Cydnidae), leaf beetle Gastrophysa atrocyanea Motschulsky (Coleoptera: Chrysomelidae) and the Japanese oak silkworm Antheraea yamamai (Lepidoptera: Saturniidae), all of which fast for more than 6 months as part of their life-history strategy. Resulting diet-consumer nitrogen isotope discrimination during fasting ranged from 0 to 7 parts per thousand, as in many commonly known terrestrial arthropods. We conclude that prolonged fasting of arthropods does not always result in anomalous diet-consumer nitrogen isotope fractionation, since the recycling process is closed or nearly closed with respect to nitrogen isotopes.

• 出版日期2011