Structural organization of excretory organs in Phasmatodea based on micro-computed tomography

Phasmatodea excretory organs differ from other insects’. They consist of two types of Malpighian tubules, excretory and calciferous, and the enigmatic midgut appendages, which are an autapomorphy of this lineage. To gain a better understanding of these three tubules, we used micro-computed tomography to visualize their structural organization in a female Epidares nolimetangere. The midgut appendices were conspicuous, with ducts arising from their ampules penetrating the midgut wall and connecting to the exoperitrophic space. Radio-dense material was observed in the calciferous Malpighian tubules, differentiating them from the excretory Malpighian tubules. While their key role in the development of the biomineralized eggs of Phasmatodea is assumed, the process of how this material is transferred to the eggshells remains unclear. These observations validate previous anatomic and microscopy findings of the Phasmatodea excretory tubules with the description of the structural organization of the excretory organs in a species so far not examined in this regard.