Rork Adam M, Mikó István, Renner Tanya
The Pennsylvania State University, Department of Entomology, University Park, PA 16802, USA.
The University of New Hampshire, College of Life Science and Agriculture, Durham, NH, 03824, USA.
Arthropod Struct Dev. 2019 Mar;49:19-25. doi: 10.1016/j.asd.2018.12.004. Epub 2019 Feb 22.
The pygidial gland system is a key innovation in adephagan beetles, producing, storing, and spraying defensive chemical compounds. As the source of defensive chemical production and storage, the pygidial gland system experiences severe chemical stress which challenges the integrity of the entire gland system. Here, we utilize autofluorescence-based confocal laser scanning microscopy to examine the morphology of pygidial gland secretory lobes and collecting ductules in a common Pennsylvanian harpaline species, Harpalus pensylvanicus. The glandular units are composed of type-III exocrine cells which empty into resilin-rich ductules, which themselves lead into a larger resilin-rich collecting duct, and ultimately the pygidial reservoir pump. We also utilize histological staining with toluidine blue and brightfield imaging to provide additional support for the presence of resilin in the collecting duct, as toluidine blue has been shown to stain resilin without metachromasia. We hypothesize that the high resilin content of the collecting ducts might be a widespread key evolutionary adaptation to prevent damage caused by physical and chemical stress generated in pump-containing insect exocrine gland systems.
臀腺系统是肉食亚目甲虫的一项关键创新，用于产生、储存和喷射防御性化合物。作为防御性化合物产生和储存的源头，臀腺系统承受着严重的化学压力，这对整个腺体系统的完整性构成了挑战。在此，我们利用基于自发荧光的共聚焦激光扫描显微镜，研究宾夕法尼亚州常见的步甲科物种宾夕法尼亚步甲（Harpalus pensylvanicus）的臀腺分泌叶和收集小管的形态。腺单位由III型外分泌细胞组成，这些细胞排入富含弹性蛋白的小管，这些小管又通向一个更大的富含弹性蛋白的收集管，最终通向臀腺储液泵。我们还利用甲苯胺蓝组织学染色和明场成像，为收集管中存在弹性蛋白提供额外支持，因为甲苯胺蓝已被证明能对弹性蛋白进行染色而不产生异染性。我们推测，收集管中高含量的弹性蛋白可能是一种广泛存在的关键进化适应性特征，以防止含泵昆虫外分泌腺系统中产生的物理和化学压力造成损害。
