Dungait Jennifer A J, Briones Maria J I, Bol Roland, Evershed Richard P
Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, University of Bristol, School of Chemistry, Cantocks Close, Bristol BS8 1TS, UK.
Rapid Commun Mass Spectrom. 2008 Jun;22(11):1643-52. doi: 10.1002/rcm.3455.
Litter-dwelling (epigeic) Lumbricus rubellus and soil-dwelling (endogeic) Allolobophora chlorotica earthworms were observed aggregating under C(3) (delta(13)C = -31.3 per thousand; delta(15)N = 10.7 per thousand) and C(4) (delta(13)C = -12.6 per thousand; delta(15)N = 7.5 per thousand) synthetic dung pats applied to a temperate grassland (delta(13)C = -30.3 per thousand; delta(15)N = 5.7 per thousand) in an experiment carried out for 372 days. Bulk delta(13)C values of earthworms collected from beneath either C(3) or C(4) dung after 28, 56, 112 and 372 days demonstrated that (i) L. rubellus beneath C(4) dung were significantly (13)C-enriched after 56 days (delta(13)C = -23.8 per thousand) and 112 days (delta(13)C = -22.4 per thousand) compared with those from C(3) dung treatments (56 days, delta(13)C = -26.5 per thousand; 112 days, delta(13)C = -27.0 per thousand), and (ii) A. chlorotica were 2.1 per thousand (13)C-enriched (delta(13)C = -24.2 per thousand) relative to those from C(3) dung (delta(13)C = -26.3 per thousand) treatments after 372 days. Bulk delta(15)N values did not suggest significant uptake of dung N by either species beneath C(3) or C(4) dung, but showed that the endogeic species (total mean delta(15)N = 3.3 per thousand) had higher delta(15)N values than the epigeic species (total mean delta(15)N = 5.4 per thousand). Although the two species exhibited similar fatty acid profiles, individual fatty acid delta(13)C values revealed extensive routing of dietary C into body tissue of L. rubellus, but minor incorporation into A. chlorotica. In particular, the direct incorporation of microbial biomarker fatty acids (iC(17:0), aC(17:0)) from (13)C-labelled dung in situ, the routing of dung C into de novo synthesised compounds (iC(20:4)(omega)(6),C(20:5)(omega)(3), and the assimilation of essential fatty acids ((C(18:1)(omega)(9), C(18:1)(omega(7), C(18:2)(omega(6), C(18:3)(omega)(3)) derived from dung, were determined.
在一项为期372天的实验中，观察到生活在落叶层（地表）的赤子爱胜蚓（Lumbricus rubellus）和生活在土壤中（内栖）的绿正蚓（Allolobophora chlorotica）在施用于温带草原（δ¹³C = -30.3‰；δ¹⁵N = 5.7‰）的C₃（δ¹³C = -31.3‰；δ¹⁵N = 10.7‰）和C₄（δ¹³C = -12.6‰；δ¹⁵N = 7.5‰）合成粪便块下聚集。在28天、56天、112天和372天后，从C₃或C₄粪便下收集的蚯蚓的总体δ¹³C值表明：（i）与C₃粪便处理组（56天，δ¹³C = -26.5‰；112天，δ¹³C = -27.0‰）相比，C₄粪便下的赤子爱胜蚓在56天（δ¹³C = -23.8‰）和112天（δ¹³C = -22.4‰）后显著富集¹³C；（ii）372天后，绿正蚓相对于C₃粪便处理组（δ¹³C = -26.3‰）的蚯蚓¹³C富集了2.1‰（δ¹³C = -24.2‰）。总体δ¹⁵N值并未表明C₃或C₄粪便下的任何一个物种显著吸收了粪便中的氮，但表明内栖物种（总平均δ¹⁵N = 3.3‰）的δ¹⁵N值高于地表物种（总平均δ¹⁵N = 5.4‰）。尽管这两个物种表现出相似的脂肪酸谱，但单个脂肪酸的δ¹³C值显示，饮食中的碳大量进入了赤子爱胜蚓的身体组织，但进入绿正蚓的较少。特别是，原位测定了来自¹³C标记粪便的微生物生物标志物脂肪酸（iC₁₇:₀，aC₁₇:₀）的直接掺入、粪便碳进入新合成化合物（iC₂₀:₄(ω)₆，C₂₀:₅(ω)₃）的途径以及来自粪便的必需脂肪酸（(C₁₈:₁(ω)₉，C₁₈:₁(ω)₇，C₁₈:₂(ω)₆，C₁₈:₃(ω)₃）的同化情况。
