title: Changes in the midgut diverticula in the harvestmen Amilenus aurantiacus (Phalangiidae, Opiliones) during winter diapause.
abstract: The harvestmen Amilenus aurantiacus overwinter in diapause in hypogean habitats. The midgut diverticula have been studied microscopically (light microscopy, TEM) and biochemically (energy-storing compounds: lipids and glycogen) to analyze changes during this programmed starvation period. Throughout the investigated period, the epithelium of the midgut diverticula is composed of secretory cells, digestive cells and adipocytes. Additionally, after the middle of overwintering, the excretory cells appear, and two assemblages of secretory cells are present: the SC1 secretory cells are characterized by electron-dense cytoplasm with numerous protein granules, and the SC2 cells by an electron-lucent cytoplasm with fewer protein granules. The autophagic activity is observed from the middle of overwintering, indicating its vital role in providing nutrients during this non-feeding period. Lipids and glycogen are present in the midgut diverticula cells, except in the excretory cells. Measurements of the lipid droplet diameters and the lipid quantities yielded quite comparable information on their consumption. Lipids are gradually spent in both sexes, more rapidly in females, owing to ripening of the ovaries. Glycogen rates decrease towards the middle, and increase just before the end of overwintering, indicating that individuals are preparing for the epigean active ecophase.
authors.affiliation: Medical Faculty, University of Maribor, Taborska ulica 8, SI-2000 Maribor, Slovenia; Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia; Faculty of Chemistry and Chemical Engineering, Smetanova ulica 17, University of Maribor, SI-2000 Maribor, Slovenia. Electronic address: sasa.lipovsek@uni-mb.si.
authors.forename: Saška
authors.initials: S
authors.lastname: Lipovšek
authors.affiliation: Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia.
authors.forename: Tone
authors.initials: T
authors.lastname: Novak
authors.affiliation: Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia.
authors.forename: Franc
authors.initials: F
authors.lastname: Janžekovič
authors.affiliation: Institute of Cell Biology, Histology and Embryology, Research Unit Electron Microscopic Techniques, Medical University of Graz, Harrachgasse 21, Graz A-8010, Austria. Electronic address: gerd.leitinger@medunigraz.at.
authors.forename: Gerd
authors.initials: G
authors.lastname: Leitinger
mesh_terms: D000818:Animals; D001097:Arachnida / Q000166:cytology / Q000648:ultrastructure*; D064666:Diapause, Insect; D004064:Digestive System / Q000166:cytology / Q000648:ultrastructure; D005260:Female; D050356:Lipid Metabolism; D008297:Male; D012621:Seasons
keywords: Arachnids; Autophagy; Diapause; Glycogen; Lipids; Ultrastructure