Fig 1.
A part of the Malpighian tubule (MT) of T. cavicola at the beginning of overwintering.
Light microsccopy allows to see the general appearance of a MT composed of the epithelium (EP), and the lumen (LU).
Fig 2.
Semithin cross-section of the Malpighian tubule (MT) in T. cavicola (a) and T. neglectus (b) at the beginning of overwintering.
The epithelium is composed of columnar epithelial cells (EC) and underlying basal lamina (BL). The apical plasma membrane of the ECs is differentiated into the brush border (BB). The cytoplasm is filled with numerous spherites (S). LU, lumen of the MT; MC, individual muscle cells; N, nucleus of the epithelial cell. Note that this figure shows an oblique transection of the MT.
Table 1.
Rates (in %) of the Malpighian tubule epithelial cell samples containing autophagic structures in Troglophilus cavicola and T. neglectus during overwintering, observed by TEM.
Fig 3.
Ultrathin cross-section of the Malpighian tubule (MT) in T. cavicola at the beginning of overwintering.
(a) The apical part of the epithelial cell with numerous mitochondria (M) and spherites (S). The apical plasma membrane is differentiated into microvilli of up to 5 μm long (MV). LU, lumen of the MT. (b) The perinuclear cytoplasm containing many mitochondria (M) and spherites (S). (c) The basal part of the epithelial cell with spherites (S) and mitochondria (M). The basal plasma membrane with typical multiple infoldings and a few mitochondria. Muscle cell (MC) beneath the epithelium of the MT. BL, basal lamina. (d) Golgi apparatus (GA) and mitochondria (M) in the perinuclear region of the epithelial cell. Scale bar: 2 μm (a, b, c) and 500 nm (d).
Fig 4.
IFM-Visualization of autophagosomes labelled with antiserum against LC3.
Immunofluorescent images show autophagosomes (arrows) in the epithelial cells of the Malpighian tubules of T. cavicola at the beginning of the overwintering (a), in the middle (b) and at the end of overwintering (c).
Fig 5.
Ultrathin cross-section of the Malpighian tubule (MT) in T. cavicola in the middle of overwintering.
(a) Apical part of the cell with numerous mitochondria (M). Spherites (S) containing electron-lucent concentric layers. MV, microvilli. Scale bar: 2 μm. (b) Perinuclear region of the epithelial cell with mitochondria (M) and spherites (S). Scale bar: 1 μm. (c) The basal part of the epithelial cell with the nucleus (N), spherites (S) and mitochondria (M). MC, muscle cell. Scale bar: 2 μm. (d) A spherite (S) composed of electron-lucent and electron-dense concentric layers. Scale bar: 500 nm.
Fig 6.
Ultrathin cross-section of the Malpighian tubule (MT) in T. cavicola in the middle (a, b) and at the end of overwintering (c, d).
(a) Autophagosome (AP) composed of granular electron-dense material and fragments of the membranes. Scale bar: 500 nm. Inset: the phagophore (arrow). Scale bar: 500 nm. (b) Autolysosome (AL). Scale bar: 500 nm. (c) Autophagosome (AP), a spherite (S) and a mitochondrium (M) in the perinuclear cytoplasm. Scale bar: 500 nm. (d) Autophagosome (AP) containing material of variable electron density. Scale bar: 500 nm. Inset: a residual body (RB) and a mitochondrium (M). Scale bar: 500 nm.
Fig 7.
Ultrathin cross-section of the Malpighian tubule (MT) in T. cavicola at the end of overwintering.
(a) Epithelial cells (EC) and a muscle cell (MC). Fully-formed spherite in which the dense core is in a contact with the membrane (1). Cases of gradually exploited spherites (2–5). In 2 and 3 the dense spherital cores lost the contact with the membrane. In 4, only one concentric ring of the spherite material and the membrane could be recognized. In 5, the dense core of the spherite is completely exploited; only the membrane is present. LU, lumen of the MT; S, spherite. Scale bar: 2 μm. (b) The perinuclear region of the EC with spherites (S). Scale bar: 1 μm. (c) Apical part of the EC. LU, lumen of the MT; M, mitochondrium; S, spherite. Scale bar: 2 μm. (d) Basal part of the EC and the basal lamina (BL). S, spherite. Scale bar: 2 μm.
Table 2.
Descriptive statistics (mean ± StD; min − max) of autophagosome abundances per 100 μm2 in the epithelial cells of the Malpighian tubules in Troglophilus cavicola and T. neglectus, and Mann-Whitney U test between the sexes.
Significant differences in bold.
Table 3.
Differences in autophagosome abundances per 100 μm2 in the epithelial cells between each sex of Troglophilus cavicola and T. neglectus using Mann-Whitney U test.
Significant differences in bold.
Fig 8.
Abundances of autophagosomes per 100 μm2 in the epithelial cells of the Malpighian tubules in Troglophilus cavicola and T. neglectus during three time frames of overwintering, as determined using IFM.