Aus dem Forschungsinstitut für Wildtierkunde und Ökologie der Veterinärmedizinischen Universität Wien Vorstand: O. Univ. Prof. Dr. rer. nat. W. Arnold A - 1160 Wien, Savoyenstraße 1 Seasonal changes in liver size in edible dormice (Glis glis): non-invasive measurements using ultrasound INAUGURAL-DISSERTATION zur Erlangung der Würde eines DOCTOR MEDICINAE VETERINARIAE der Veterinärmedizinischen Universität Wien vorgelegt von Mag. Katharina Außerlechner Wien, 2009 Wissenschaftliche Betreuung: Ao. Univ. Prof. Dr. rer. nat. Thomas Ruf Forschungsinstitut für Wildtierkunde und Ökologie 1. Gutachter: Ao. Univ. Prof Dr. rer. nat. Thomas Ruf Forschungsinstitut fiir Wildtierkunde und Ökologie 2. Gutachter: Ao. Univ. Prof Dr. med. vet. Tzt. Sibylle Kneissl Department fur Kleintiere und Pferde Klinik für Bildgebende Diagnostik Tag der mündlichen Prüfung: 10. Juni 2009 Gewidmet meiner Familie Hubert, Maria, Hubi und Lisi TABLE OF CONTENTS LIST OF ABBREVIATIONS 1 LIST OF FIGURES 2 LIST OF TABLES 5 1. INTRODUCTION 6 2. MATERIAL AND METHODS 9 2.1 INVESTIGATED SPECIES 9 2.2 STRUCTURE AND COURSE OF THE STUDY 11 2.2.1 Study period 11 2.2.2 Classification of age classes and identification of individuals 11 2.2.3 Study areas // 2.3 ULTRASONOGRAPHIC EXAMINATION 13 2.3.1 The dissection 13 2.3.2 Principles of ultrasonographic examination 14 2.3.3 Fixation of the edible dormice 17 2.3.4 Ultrasonography of the animals using "LOGIQ e" 18 2.4 STATISTICAL ANALYSES 21 3. RESULTS 22 3.1 ENCLOSURES-HOUSED ANIMALS 22 3.1.1 Body mass 22 3.1.2 Liver size 24 3.1.3 Gallbladder 28 u 3.2 FREE-LIVING ANIMALS 31 3.2.! Body mass 31 3.2.2 Liver 33 3.2.3 GallMadder 35 3.3 MAIN ULTRASONOGRAPHIC ARTEFACTS 36 4. DISCUSSION 37 4.1 INTERNAL ORGANS 37 4.2 BODY MASS 42 4.3 ULTRASONOGRAPH Y 42 5. ABSTRACT 46 6. ZUSAMMENFASSUNG 47 7. ACKNOWLEDGEMENT 48 8. REFERENCES 49 LIST OF ABBREVIATIONS ANOVA analysis of variance DF degrees of freedom Fig. Figure FIWI Research Institute of Wildlife Ecology GIT gastrointestinal tract Ime linear mixed effect model L. Lx)bus L. hep. dext. med./lat. Lobus hepatis dexter medialis/lateralis L. hep. sin. med./lal. Lobus hepatis sinister medialis/lateralis MHz megahertz N number of examined animals N. number of examined adults Nf number of examined females N„ number of examined males number of examined yearlings SEM standard error of the mean Tab. Table LIST OF FIGURES Fig. 1 Edible dormice sitting in a nest box at the Institute (FlWl) 10 Fig. 2 Edible dormice retreat to underground burrows to survive the hibernation period..... 10 Fig. 3 Nest box in the woodland. The nest boxes were fixed 1.5 - l.S m above ground and were checked fortnightly. 12 Fig. 4 Liver of an edible dormouse: length (green arrow) and height (black arrow). Unfortu- nately the lobes of the right side were not in correct position. Fades visceralis of the left lateral lobe (1), left medial lobe (2), right medial lobe (4), quadrate lobe (5), cau- date lobe (6). gallbladder (7): Fades dorsalis of the right lateral lobe (3); 13 Fig. 5 Anatomical illustration of the liver in an edible dormouse. Left lateral lobe (L. hep. sin. lat.; black, dotted line), lefi medial lobe (L. hep. sin. med.; black, broken line), right lateral lobe (L. hep. dext. lat.; orange, dotted line), right medial lobe (L. hep. dext. med.; orange, broken line), caudate lobe (L. caudatus; blue, broken line), quadrate lobe (L. quadratus; blue line), gallbladder (green, dotted line), left kidney (orange), vertebra and ribs (black) 14 Fig 6 Anatomical illustration of the abdomen, left lobe (black lines), quadrate lobe (blue, broken line), gallbladder (green, dotted line), stomach (brown), intestine (brown, bro- ken line), spleen (red), left kidney (orange), urinary bladder (yellow), costal arch (black line) 15 Fig. 7 shows a folded funnel-formed cotton bag for the fixation of the animals (brown). A Vel- cro fastener (orange), locking the bags at the longitudinal side, allowed an unprob- lematic release of the edible dormice. Through re-closable windows (dotted lines) at both sides the abdomen and the liver could be examined. 17 Fig. 8 Ultrasonographic image of the liver, transverse view. A "W-formed image of the liver occurred on the screen. The "W"-shaped liver occurred because of the left (on the right side of the screen) and right liver lobe (on the left side of the screen). For meas- uring the" transverse" liver size a vertical line directly in the middle of the "W" from the dorsal to the ventral side was drawn. From the ventral end of the vertical line an- other line was drawn in a 45-degree angle towards the left and right edge of the liver lobes 19 Fig. 9 Ultrasonographic image of the liver, sagittal view. From the dorsal margin of the lobe a I cm vertical line was drawn in a ventral direction and the horizontal line to this first line was measured. 20 Fig. 10 Seasonal change of body mass in adult edible dormice. Both males (black circles) and females (red circles) showed seasonal fluctuations in body mass. Adult females had generally less weight than adult males. Close to the beginning of hibernation (Sep- tember) only three adult males and four adult females were captured- A total of 35 adults at the Institute were examined. Means ± SEM. 23 Fig. 11 Seasonal change of body mass in enclosure-housed yearlings. Both males and females gained weight over the active season. Means ± SEM. 24 Fig. 12 Seasonal change of the right liver measurement in one adult male and one adult fe- male. The decrease from June to July in the adult females may have been caused by mating and lactating. Medians of repeated measurements per month 25 Fig. 13 Seasonal change of the right liver measurement (pooled data for adults and year- lings). In all examined individuals a seasonal increase of the liver size was deter- mined. Means ±SEM. 26 Fig. 14 A significant interaction between body mass and month was observed. Animals with less weight had a smaller right liver measurement at the beginning of the active sea- son (May - July). Later in season (August - September) the relation between right liver measurement and body mass was weaker 27 Fig. IS Correlation of the right and left liver measurement in females and males (pooled data for adults and yearlings). Pearson's correlation for all data points: r^ = 0.79, p < O.OOOI 28 Fig. 16 Correlation between gallbladder volume and body mass. Pearson's correlation; H - 0.26. p < 0.0001 29 Fig. 17 Seasonal change of the gallbladder volume (pooled data for males and Jemales). Means ± SEM of repeated measurements per month 30 Fig. 18 Mean gallbladder volume of males and females. Means ± SEM. 30 Fig. 19 Mean gallbladder volume of adults and yearlings. Means ± SEM. 31 Fig. 20 Seasonal change of body mass in edible dormice of the woodland. The values of each investigation were shown 32 Fig. 21 Mean body mass in enclosure-housed and free-living individuals. Means ±SEM. 33 Fig. 22 Values of each investigation of the right liver measurement in free-living edible dor- mice 34 Fig, 23 Sagittal liver size in enclosure-housed and free-living individuals. Means ± SEM. 35 LIST OF TABLES Table I Taxonomy of the edible dormouse (WILSON and REEDER, 1993) 9 Table 2 ANOVA table for effects of age-class, sex and month of the year on body mass. Non-significant terms were removed from the model. 22 Table 3 ANOVA table for effects of month of the year and body mass on right liver measure- ment 26 Table 4 ANOVA table for effects of body mass, month of the year, sex and age on the gall- bladder volume. Non-significant terms were removed from the model 29 Table 5 ANOVA table for effects of the study area on the body mass 33 Table 6 ANOVA results on sagittal liver size: Sagittal liver size was only affected by study area, and independent of all other factors, including body mass 35 Table 7 ANOVA table: The gallbladder volume was significantly affected by the body mass. Non-significant terms were removed from the model. 36 1. INTRODUCTION Edible dormice (Glis glis) are small mammalian hibemators distributed in Central Europe. The hibernation season is extremely long in this species (~ 8 months), at least in the northern part of their distribution area (BIEBER and RUF, 2009b). After emerging, the dormouse's nutrition consists of different fruits and leaves whereas fatty seeds (e.g., beech nuts) are their main food source close to the end of their active season (FIETZ et al., 2005; RUF et al., 2006). Mainly caused by the long hibernation season dormice show strong seasonal fluctua- tions in body mass. Actually, edible dormice lose about one third of their body mass during hibernation (COCHET et al, 1999; FIETZ et al., 2005). A significant reduction of body mass is also shown in other hibemators. For example, echidnas {Echidna aculeata) lose about one fifth of their body mass after 5 month of hibernation (FALKENSTEIN et al., 2001). A good body condition after emergence seems to be very important for the dormouse's fertility. PI- LASTRO et al. (1994) detected that, dormice in good body condition breed earlier than those in bad condition. After mating body mass constantly increases until it reaches, mainly due to fat accumulation, a maximum before the onset of hibemation. As a typical hibemator, the edible dormouse reduces its metabolism extremely during hibemation. Blood circulation and, accordingly, organ functions are reduced during this period of hypometabolism (HERZOG, 1966; KEUSER, 1967; BIEBER, 1998; FIETZ et al, 2004).