OD Taxonomy and Phylogeny, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, 1000, Brussels, Belgium.
, San Ramon Drive 1067, 95973-1026, Chico, CA, USA.
Naturwissenschaften. 2023 Mar 27;110(2):13. doi: 10.1007/s00114-023-01841-0.
Several sawfly species (Hymenoptera: Symphyta) possess larval stages with oesophageal diverticula in which plant compounds are sequestered and used for defence against predators. These organs are present in the larvae of Susana (Tenthredinidae) but remain poorly studied. Here, the aim was to analyse the diverticula extract of Susana cupressi by gas chromatography-mass spectrometry to better understand the ecology of this species. The foliage of the hostplant (Cupressus sempervirens), as well as the larval foregut, midgut, and haemolymph were also analysed. Complementary data were gathered by morphological observations, bioassays using ants, and genetic analyses to identify the studied Susana species. Altogether, 48 terpenes were identified, 30 being sesquiterpenes. The terpenes were generally detected in the foliage, but also in the diverticula, foregut, and midgut, whereas none of them in the haemolymph. The main compounds were alpha-cedrene, alpha-fenchene, alpha-pinene, alpha-terpinyl acetate, beta-myrcene, beta-pinene, cedrol, delta 3-carene, epi-bicyclosesquiphellandrene, germacrene D, limonene, sabinene, and terpinolene. The chemical profiles of these 13 compounds were significantly correlated between foliage-diverticula, diverticula-foregut and foregut-midgut, but not correlated for the three remaining possible comparisons. Alpha-pinene decreased and germacrene D increased from the foliage to the diverticula, which may reflect a specific sequestration of the latter terpene and its known deleterious effects on insects. We conclude that larvae of S. cupressi, similarly to those of diprionids, are well defended against predatory attacks by sequestering and regurgitating hostplant terpenes, including germacrene D.
几种叶蜂（膜翅目：叶蜂科）具有食管憩室的幼虫阶段，其中植物化合物被隔离并用于防御捕食者。这些器官存在于 Susana（松叶蜂科）的幼虫中，但研究甚少。在这里，目的是通过气相色谱-质谱法分析 Susana cupressi 的憩室提取物，以更好地了解该物种的生态学。还分析了寄主植物（柏木）的叶片，以及幼虫的前肠、中肠和血淋巴。通过形态观察、使用蚂蚁进行的生物测定以及用于鉴定所研究的 Susana 物种的遗传分析收集了补充数据。总共鉴定出 48 种萜烯，其中 30 种为倍半萜烯。萜烯通常在叶片中检测到，但也在憩室、前肠和中肠中检测到，而在血淋巴中则未检测到。主要化合物为α-雪松烯、α-茴香脑、α-蒎烯、α-松油醇乙酸酯、β-月桂烯、β-蒎烯、柏木醇、δ 3-蒈烯、表双环[4.2.0]-2,4,7-三烯、环倍半水芹烯、大根香叶烯 D、柠檬烯、侧柏烯和萜品烯。这 13 种化合物的化学图谱在叶片-憩室、憩室-前肠和前肠-中肠之间呈显著相关，但在其余三种可能的比较中则无相关性。α-蒎烯从前肠到憩室减少，大根香叶烯 D 增加，这可能反映了后者萜烯的特异性隔离及其对昆虫的已知有害影响。我们得出结论，类似于双翅目 Diprionidae 的幼虫，通过隔离和反刍寄主植物萜烯，包括大根香叶烯 D，它们很好地防御了捕食者的攻击。
