Ultrathin cross-section of the Malpighian tubule (MT) in <i>T</i>. <i>cavicola</i> in the middle of overwintering.

<p><b>(a)</b> Apical part of the cell with numerous mitochondria (M). Spherites (S) containing electron-lucent concentric layers. MV, microvilli. Scale bar: 2 μm. <b>(b)</b> Perinuclear region of the epithelial cell with mitochondria (M) and spherites (S). Scale bar: 1 μm. <b>(c)</b> The basal part of the epithelial cell with the nucleus (N), spherites (S) and mitochondria (M). MC, muscle cell. Scale bar: 2 μm. <b>(d)</b> A spherite (S) composed of electron-lucent and electron-dense concentric layers. Scale bar: 500 nm.