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  • 1.
    Abreu-Vieira, Gustavo
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Regulation and measurement of brown adipose tissue blood flow2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Brown adipose tissue (BAT) is an organ specialized in macromolecule combustion in order to produce heat. Because of its high capacity to dissipate energy, it is currently among the best hopes for future treatments of obesity and diabetes. BAT is permeated by a vast capillary network that delivers blood rich in oxygen and nutrients to supply the high metabolic needs of the tissue. At the same time, metabolites, carbon dioxide and warm blood are drained back into systemic circulation. Blood flow is in fact a limiting factor for thermogenesis. Therefore, understanding BAT blood flow regulation is a crucial step for describing the tissue function. This thesis aims to summarize anatomical descriptions, to discuss the methodological evolution of the field, and to synthetize what we have learned about mechanistic regulation of BAT blood flow during the last half century. Manuscript I introduces a new method (high-resolution laser-doppler imaging) for the measurement of BAT blood flow, and gives mechanistic insights about its physiological regulation. Manuscript II focuses on the influence of bombesin receptor subtype-3 on the neurological control of body temperature and thermogenesis.

  • 2.
    Ackefors, Hans
    Stockholm University.
    Studies on the ecology of the zooplankton fauna in the Baltic proper1971Doctoral thesis, comprehensive summary (Other academic)
  • 3.
    Ackefors, Hans
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    The evolution of a worldwide shrimp industry2009In: World Aquaculture, ISSN 1041-5602, Vol. 40, no 3, p. 46-55Article in journal (Refereed)
  • 4. Aguirre, A. A.
    et al.
    Angerbjörn, A.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Mörner, T.
    Health evaluation of arctic fox (Alopex lagopus) cubs in Sweden2000In: Journal of zoo and wildlife medicine, ISSN 1042-7260, E-ISSN 1937-2825, Vol. 31, no 1, p. 36-40Article in journal (Refereed)
    Abstract [en]

    Hematologic. serum biochemistry, and serum cortisol reference ranges were established and tonsil/rectal bacterial and fecal parasite examinations were performed on 21 wild arctic fox (Alopex lagopus) cubs during July 1996. Several of the hematologic and serum biochemistry values fell within normal ranges for other wild canids or domestic dogs of the same age class. Serum alanine transaminase and creatine phosphokinase values were significantly higher in the youngest cubs. Proteus vulgaris and Escherichia coli were isolated from both tonsilar and rectal swabs of several cubs in all dens. The most common gastrointestinal parasite ova were Toxascaris leonina (59%), Isospora spp. (52%), Uncinaria stenocephala (33%), and Capillaria spp. (26%). Prevalence of T. leonina differed significantly between dens and between age groups. Hematologic and serum biochemistry values and degree of parasitism may be indicators of health, stress, and nutritional status of arctic foxes.

  • 5. Aguirre, A. Alonso
    et al.
    Principe, B.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Mörner, Torsten
    Field anesthesia of wild arctic fox (Alopex lagopus) cubs in the Swedish lapland using medetomidine-ketamine-atipamezole2000In: Journal of zoo and wildlife medicine, ISSN 1042-7260, E-ISSN 1937-2825, Vol. 31, no 2, p. 244-246Article in journal (Refereed)
    Abstract [en]

    A safe and effective anesthetic regime for use in arctic fox (Alopex lagopus) cubs was developed. During July 1996, six free-ranging 6-8-wk-old cubs were captured near their den in Vindelfjallen Nature Reserve, Sweden. Medetomidine and ketamine HCl, followed by atipamezole, were selected for the anesthetic trial because of the well-documented safety and efficacy of this drug combination in a broad range of species. The dosage regimen used was 50 mu g/kg medetomidine combined with 2.5 mg/kg ketamine followed by reversal with 250 mu g/kg atipamezole. induction was rapid, with a mean induction time of 1 min and 32 sec (range: 58-150 sec). The cubs were anesthetized for a mean time of 18 +/- 5 min (range: 13-25 min). Serially recorded heart rate, respiratory rate, temperature, and pulse oximetry were stable throughout the anesthetic period for all cubs. Anesthetic depth was suitable for safe handling and minor clinical procedures, including venipuncture. Following atipamezole, all cubs were standing within 12 +/- 7 min (range: 5-24 min) and fully recovered at 27 +/- 5 min (range: 19-36 min). This information will be useful for future captive breeding and management programs involving the endangered arctic fox.

  • 6.
    Ah-King, Malin
    Stockholm University.
    Phylogenetic analyses of parental care evolution2003Doctoral thesis, comprehensive summary (Other academic)
  • 7.
    Ahlbert, Inga-Britt
    Stockholm University.
    Organization of the cone cells in the retinae of some teleosts in relation to their feeding habits1975Doctoral thesis, comprehensive summary (Other academic)
  • 8.
    Ahnlund, Hans
    Stockholm University.
    Aspects of the population dynamics of the badger (Meles meles L.)1980Doctoral thesis, comprehensive summary (Other academic)
  • 9. Ahola, Virpi
    et al.
    Lehtonen, Rainer
    Somervuo, Panu
    Salmela, Leena
    Koskinen, Patrik
    Rastas, Pasi
    Valimaki, Niko
    Paulin, Lars
    Kvist, Jouni
    Wahlberg, Niklas
    Tanskanen, Jaakko
    Hornett, Emily A.
    Ferguson, Laura C.
    Luo, Shiqi
    Cao, Zijuan
    de Jong, Maaike A.
    Duplouy, Anne
    Smolander, Olli-Pekka
    Vogel, Heiko
    McCoy, Rajiv C.
    Qian, Kui
    Chong, Wong Swee
    Zhang, Qin
    Ahmad, Freed
    Haukka, Jani K.
    Joshi, Aruj
    Salojarvi, Jarkko
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Grosse-Wilde, Ewald
    Hughes, Daniel
    Katainen, Riku
    Pitkanen, Esa
    Ylinen, Johannes
    Waterhouse, Robert M.
    Turunen, Mikko
    Vaharautio, Anna
    Ojanen, Sami P.
    Schulman, Alan H.
    Taipale, Minna
    Lawson, Daniel
    Ukkonen, Esko
    Makinen, Veli
    Goldsmith, Marian R.
    Holm, Liisa
    Auvinen, Petri
    Frilander, Mikko J.
    Hanski, Ilkka
    The Glanville fritillary genome retains an ancient karyotype and reveals selective chromosomal fusions in Lepidoptera2014In: Nature Communications, E-ISSN 2041-1723, Vol. 5, p. 4737-Article in journal (Refereed)
    Abstract [en]

    Previous studies have reported that chromosome synteny in Lepidoptera has been well conserved, yet the number of haploid chromosomes varies widely from 5 to 223. Here we report the genome (393 Mb) of the Glanville fritillary butterfly (Melitaea cinxia; Nymphalidae), a widely recognized model species in metapopulation biology and eco-evolutionary research, which has the putative ancestral karyotype of n = 31. Using a phylogenetic analyses of Nymphalidae and of other Lepidoptera, combined with orthologue-level comparisons of chromosomes, we conclude that the ancestral lepidopteran karyotype has been n = 31 for at least 140 My. We show that fusion chromosomes have retained the ancestral chromosome segments and very few rearrangements have occurred across the fusion sites. The same, shortest ancestral chromosomes have independently participated in fusion events in species with smaller karyotypes. The short chromosomes have higher rearrangement rate than long ones. These characteristics highlight distinctive features of the evolutionary dynamics of butterflies and moths.

  • 10. Alexander, Jodi L.
    et al.
    Oliphant, Andrew
    Wilcockson, David C.
    Brendler-Spaeth, Timothy
    Dircksen, Heinrich
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Webster, Simon G.
    Pigment dispersing factors and their cognate receptors in a crustacean model, with new insights into distinct neurons and their functions2020In: Frontiers in Neuroscience, ISSN 1662-4548, E-ISSN 1662-453X, Vol. 14, article id 595648Article in journal (Refereed)
    Abstract [en]

    Pigment dispersing factors (PDFs, or PDHs in crustaceans) form a structurally related group of neuropeptides found throughout the Ecdysozoa and were first discovered as pigmentary effector hormones in crustaceans. In insects PDFs fulfill crucial neuromodulatory roles, most notably as output regulators of the circadian system, underscoring their central position in physiological and behavioral organization of arthropods. Intriguingly, decapod crustaceans express multiple isoforms of PDH originating from separate genes, yet their differential functions are still to be determined. Here, we functionally define two PDH receptors in the crab Carcinus maenas and show them to be selectively activated by four PDH isoforms: PDHR 43673 was activated by PDH-1 and PDH-2 at low nanomolar doses whilst PDHR 41189 was activated by PDH-3 and an extended 20 residue e-PDH. Detailed examination of the anatomical distribution of all four peptides and their cognate receptors indicate that they likely perform different functions as secreted hormones and/or neuromodulators, with PDH-1 and its receptor 43,673 implicated in an authentic hormonal axis. PDH-2, PDH-3, and e-PDH were limited to non-neurohemal interneuronal sites in the CNS; PDHR 41189 was largely restricted to the nervous system suggesting a neuromodulatory function. Notably PDH-3 and e-PDH were without chromatophore dispersing activity. This is the first report which functionally defines a PDHR in an endocrine system in a crustacean and to indicate this and other putative roles of this physiologically pivotal peptide group in these organisms. Thus, our findings present opportunities to further examine the endocrine and circadian machinery in this important arthropod phylum.

  • 11.
    Alm Bergvall, Ulrika
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish University of Agricultural Sciences, Sweden.
    Svensson, Lisa
    Kjellander, Petter
    Vigilance adjustments in relation to long- and short term risk in wild fallow deer (Dama dama)2016In: Behavioural Processes, ISSN 0376-6357, E-ISSN 1872-8308, Vol. 128, p. 58-63Article in journal (Refereed)
    Abstract [en]

    The risk allocation hypothesis predicts that vigilance should be adjusted to the temporal variation in risk. We test this hypothesis in wild fallow deer exposed to short term (disturbance) and long term (presence of a fawn after parturition) changes in risk. We recorded the proportion, frequency and type of vigilance and size of used area before and after parturition, in GPS-collared wild female fallow deer. Vigilance was divided in two main groups: non-grazing vigilance and grazing vigilance. The latter group was divided into grazing vigilance while chewing and a grazing vigilance when chewing was interrupted. By recording external disturbance in form of passing cars, we were able to investigate if this altered the amount, and type of vigilance. We found that females increased the proportion and frequency of grazing vigilance stop chewing after parturition. The grazing vigilance chewing was unaffected, but non-grazing vigilance decreased. Disturbance increased the proportion grazing vigilance stop chewing to the same extent before and after parturition. We found a clear decrease in female home range size after parturition as a possible behavioural adjustment. The increase in grazing vigilance stop chewing after parturition is a rarely described but expected cost of reproduction.

  • 12.
    Almbro, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Impaired escape flight ability in butterflies due to low flight muscle ratio prior to hibernation2008In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 211, no 1, p. 24-28Article in journal (Refereed)
  • 13.
    Almbro, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Weight Loading and Reproductive Status Affect the Flight Performance of Pieris napi Butterflies2012In: Journal of insect behavior, ISSN 0892-7553, E-ISSN 1572-8889, Vol. 25, no 5, p. 441-452Article in journal (Refereed)
    Abstract [en]

    Weight-induced mobility reductions can have dramatic fitness consequences and winged animals are especially sensitive to the trade-off between mass and locomotion. Data on how natural weight fluctuations influence a flying insect's ability to take off are scarce. We therefore quantified take-off flight ability in Pieris napi butterflies in relation to reproductive status. Take-off flight ability (velocity and take-off angle) under suboptimal temperature conditions was recorded with a 3D-tracking camera system and was predicted to decrease with relatively larger weight loads. Our results show that relatively larger weight loads generally reduce flight speed in male butterflies and lower take-off angles in females. However, despite having a lower wing loading, mated male butterflies flew slower than unmated males. Our study suggests that retention of weight loads associated with reproduction impairs insect flight performance.

  • 14.
    Amundin, Mats
    Stockholm University, Faculty of Science, Department of Zoology.
    Sound production in odontocetes, with emphasis on the harbour porpoise, Phocoena phocoena1991Doctoral thesis, comprehensive summary (Other academic)
  • 15. Amundin, Mats
    et al.
    Carlström, Julia
    Stockholm University.
    Thomas, Len
    Carlén, Ida
    Stockholm University, Faculty of Science, Department of Zoology, Ethology. AquaBiota Water Research, Stockholm, Sweden.
    Teilmann, Jonas
    Tougaard, Jakob
    Loisa, Olli
    Kyhn, Line A.
    Sveegaard, Signe
    Burt, M. Louise
    Pawliczka, Iwona
    Koza, Radomil
    Arciszewski, Bartlomiej
    Galatius, Anders
    Laaksonlaita, Jussi
    MacAuley, Jamie
    Wright, Andrew J.
    Gallus, Anja
    Koblitz, Jens
    Dähne, Michael
    Acevedo‐Gutiérrez, Alejandro
    Benke, Harald
    Tregenza, Nick
    Wennerberg, Daniel
    Brundiers, Katharina
    Kosecka, Monika
    Tiberi Ljungqvist, Cinthia
    Jussi, Ivar
    Jabbusch, Martin
    Lyytinen, Sami
    Šaškov, Aleksej
    Blankett, Penina
    Estimating the abundance of the critically endangered Baltic Proper harbour porpoise (Phocoena phocoena) population using passive acoustic monitoring2022In: Ecology and Evolution, E-ISSN 2045-7758, Vol. 12, no 2, article id e8554Article in journal (Refereed)
    Abstract [en]

    Knowing the abundance of a population is a crucial component to assess its conservationstatus and develop effective conservation plans. For most cetaceans, abundanceestimation is difficult given their cryptic and mobile nature, especially when thepopulation is small and has a transnational distribution. In the Baltic Sea, the numberof harbour porpoises (Phocoena phocoena) has collapsed since the mid-20thcenturyand the Baltic Proper harbour porpoise is listed as Critically Endangered by the IUCNand HELCOM; however, its abundance remains unknown. Here, one of the largestever passive acoustic monitoring studies was carried out by eight Baltic Sea nationsto estimate the abundance of the Baltic Proper harbour porpoise for the first time. Bylogging porpoise echolocation signals at 298 stations during May 2011–April2013,calibrating the loggers’ spatial detection performance at sea, and measuring the clickrate of tagged individuals, we estimated an abundance of 71–1105individuals (95% CI,point estimate 491) during May–Octoberwithin the population's proposed managementborder. The small abundance estimate strongly supports that the Baltic Properharbour porpoise is facing an extremely high risk of extinction, and highlights theneed for immediate and efficient conservation actions through international cooperation.It also provides a starting point in monitoring the trend of the populationabundance to evaluate the effectiveness of management measures and determine itsinteractions with the larger neighboring Belt Sea population. Further, we offer evidencethat design-basedpassive acoustic monitoring can generate reliable estimatesof the abundance of rare and cryptic animal populations across large spatial scales.

  • 16.
    Andersson, Anastasia
    Stockholm University, Faculty of Science, Department of Zoology.
    Hidden biodiversity in an alpine freshwater top predator: Existence, characteristics, and temporal dynamics of cryptic, sympatric brown trout populations2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Intraspecific genetic diversity is imperative to the survival of species in a changing environment, and it plays a vital role in ecosystem function. Since this type of diversity can be difficult to detect it is sometimes referred to as “hidden biodiversity”. When separate and genetically distinct populations of the same species coexist within the same habitat, without apparent barriers to migration and obvious phenotypic divergence, this form of hidden biodiversity is called cryptic sympatry. Knowledge of cryptic sympatry is limited, however, and the aim of this thesis is to increase our understanding of this phenomenon by focusing on a species group where several cases of sympatry have been documented – the salmonids.

    Using the brown trout (Salmo trutta) as a model, I characterized two previously reported cases of cryptic sympatry occurring in small Swedish alpine lakes with respect to both phenotypic and genetic characteristics. I explored the hypothesis that cryptic sympatry is more common than currently recognized by reviewing literature documenting sympatry, as well as by assessing the statistical power to detect sympatric populations with varying degrees of divergence using commonly applied sample sizes for loci and individuals. Further, I performed a large-scale search for sympatric populations in alpine lakes in central Sweden.

    I found that cryptic, sympatric populations can coexist while apparently utilizing the same food resources and exhibiting the same adaptive plasticity to their shared environment (Paper I). In one of the empirical cases there were indications that the populations used different creeks for spawning, suggesting that segregation in spawning location contributes to the maintenance of sympatry (Paper II). Further, I found that differences between cryptic, sympatric populations of the same lake may be large with respect to levels of genetic diversity, inbreeding, and connectivity with populations in nearby lakes (Papers II and III). 

    I found support for the hypothesis that cryptic sympatry is more common than generally acknowledged (Papers IV and V). In the literature, cryptic sympatry is rarely reported and typically associated with higher divergence levels than between sympatric populations that differ phenotypically. My results suggest that this to a large extent may be due to limited statistical power when commonly used sample sizes in terms of individuals and loci are applied and the amount of divergence between populations is small (Paper IV). Cryptic sympatry was observed in over 40% of the screened localities (27 lakes), and was shown to be temporally stable over at least 40 years (Paper V).

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  • 17.
    Andersson, Anastasia
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Karlsson, Sten
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Mapping and monitoring genetic diversity in brown trout population systems in alpine lakes by applying newly proposed indicatorsManuscript (preprint) (Other academic)
  • 18.
    Andersson, Anastasia
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergvall, Ulrika A.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish University of Agricultural Sciences, Sweden.
    Two shades of boldness: novel object and anti-predator behavior reflect different personality dimensions in domestic rabbits2014In: Journal of ethology, ISSN 0289-0771, E-ISSN 1439-5444, Vol. 32, no 3, p. 123-136Article in journal (Refereed)
    Abstract [en]

    It is increasingly common to quantify and describe behavioral variation in domestic and wild animals in terms of personality. Correlating behavioral traits are referred to as personality dimensions or factors and different dimensions have been reported in different species. Boldness is a well-described personality dimension in several species, although some issues remain unclear. Previous models of boldness include both novelty and risk taking, but recent studies indicate that these types of behaviors may reflect separate personality dimensions. In this study, we developed a behavioral test battery for domestic rabbits, and recorded behaviors of 61 individuals in four different situations (novel object, novel arena, social, and predator interactions). We used domestic rabbits as a model because behavioral variation in rabbits has rarely been quantified in terms of personality dimensions, although rabbit behavior is described. We also wanted to investigate behavioral variation in a Swedish rabbit breed of conservation concern - the Gotland rabbit. Factor analysis of the behavioral test measures suggested three personality dimensions: exploration, boldness, and anxiety. Novel object scores clustered in the exploration and boldness factors, whereas scores associated with predator interactions were explained by anxiety, indicating that novel object and anti-predator behavior reflect different personality dimensions in rabbits.

  • 19.
    Andersson, Eva
    Stockholm University, Faculty of Science, Department of Zoology.
    Neuroendocrine control of reproduction in the three-spined stickleback, Gasterosteus aculeatus L.1992Doctoral thesis, comprehensive summary (Other academic)
  • 20. Andersson, Marica
    et al.
    Svensson, Ola
    Swartz, Terese
    Manera, Jack L.
    Bertram, Michael G.
    Stockholm University, Faculty of Science, Department of Zoology. Monash University, Australia; Swedish University of Agricultural Sciences, Sweden.
    Blom, Eva-Lotta
    Increased noise levels cause behavioural and distributional changes in Atlantic cod and saithe in a large public aquarium - A case study2023In: Aquaculture, Fish and Fisheries, ISSN 2693-8847, Vol. 3, no 5, p. 447-458Article in journal (Refereed)
    Abstract [en]

    Investigating the effects of underwater noise on aquatic animals is a research field that is receiving rapidly increasing attention. Despite this, surprisingly few studies have addressed the potential impacts of noise in a marine animal husbandry setting. In this regard, the behaviour of fish in public aquariums can be used as an indicator of well-being, and noise is known to cause behavioural changes. This case study investigates the behaviour of cod (Gadus morhua) and saithe (Pollachius virens) in a large public aquarium when exposed to increased noise levels originating from an aquarium renovation carried out by construction divers. Swimming behaviour, group formation and vertical distribution, along with yawning and scratching frequencies of the fish, were analysed from video recordings made before, during and after the exposure to increased noise levels. The same parameters were also analysed to evaluate potential effects of the presence of divers when not making renovation noise, compared to fish behaviour prior to the renovation. There was a slight change in the depth distribution of both species and a decrease in the number of scratches in cod due to the presence of divers that were not making renovation noise. In the presence of construction noises in the tank, however, both cod and saithe showed a wider array of behavioural changes, including increased swimming speed, changes in depth distribution and increased yawning frequencies. The results from this case study demonstrate that an underwater renovation with increased noise levels impacts fish behaviour and suggests that underwater noise should be considered during the management of aquatic environments, including public aquaria.

  • 21.
    Andersson, Ulf
    Stockholm University, Faculty of Science, The Wenner-Gren Institute, Physiology.
    On the biosynthesis of ATP synthase1998Doctoral thesis, comprehensive summary (Other academic)
  • 22.
    André, Carl
    Stockholm University, Faculty of Science, Department of Zoology.
    Settlement of bivalve larvae: the role of larval behavior, predation and hydrodynamics1992Doctoral thesis, comprehensive summary (Other academic)
  • 23.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Gigantism in Island Populations of Wood Mice (Apodemus) in Europe1986In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 47, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    Many rodents have large body sizes on islands, and there are many hypotheses that try to explain this observed pattern. Using body size data on Apodemus in Europe as an example, I try to evaluate the main hypotheses. These can be divided in four different categories. 1) Hypotheses assuming climatic differences between islands and mainland: no trend in body size on islands in the Mediterranean, in Britain or in the Baltic area is observed. 2) Hypotheses based on island size: no trend is observed in the data analysed. 3) Hypotheses based on distance to mainland: no general effect is found, although there is an effect in the British material. 4) Hypotheses based on faunistic differences: consistent relationships are found in all areas. A. sylvaticus shows larger body size when lacking competition from A. flavicollis or Clethrionomys glareolus or when predation is absent. A. flavicollis is larger when predators are lacking, and smaller when no competitors are present. This is in agreement with character displacement theory

  • 24.
    Angerbjörn, Anders
    Stockholm University.
    Population dynamics of mountain hares (Lepus timidus L.) on islands1986Doctoral thesis, comprehensive summary (Other academic)
  • 25.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Reproduction of Mountain Hares (Lepus-Timidus) in Relation to Density and Physical Condition1986In: Journal of Zoology, Vol. 208, no 4, p. 559-568Article in journal (Refereed)
    Abstract [en]

    Population estimates of Mountain hares were done on three islands off the west coast of Sweden. Three different relative measures of hare reproduction were negatively related to density. Most of this relationship was accounted for through a positive correlation with body condition. However, there was no significant density trend in litter size or number of litters. The start of the reproductive season each year was related to mean air temperature during spring, so when spring was early so was conception.

  • 26.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The Effect of Red Fox Predation on Mountain Hare Populations on Islands1986In: Mammal Review, ISSN 0305-1838, E-ISSN 1365-2907, Vol. 16, no 3-4, p. 198-198Article in journal (Refereed)
    Abstract [en]

    The population dynamics of Mountain Hares on islands have been monitored during 10 years. In some years Red Foxes have been present on some islands. The intensity of predation on the hares is given from the reduction of the known hare densities, and from the foxes’ diet (scat analysis). The effect of predation on the hare populations was found to be density dependent, but also dependent on the alternative food available.

    [Complete text from journal]

  • 27.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The Evolution of Body Size in Mammals on Islands - Some Comments1985In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 125, no 2, p. 304-309Article in journal (Refereed)
  • 28.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Arvidson, Bengt
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Erik
    Strömgren, Lasse
    The Effect of Winter Food on Reproduction in the Arctic Fox, Alopex-Lagopus - a Field Experiment1991In: Journal of Animal Ecology, Vol. 60, no 2, p. 705-714Article in journal (Refereed)
    Abstract [en]

    (1) The population of arctic foxes in Fennoscandia is very small and has been so for around 60 years in spite of total protection for over half a century. The reasons why the arctic fox population has not increased to its former size are unknown. The population numbers fluctuate highly in relation to vole numbers. There is also very high interannual variation in reproduction among arctic foxes. (2) To determine the effect of winter food availability on reproductive success, we carried out a feeding experiment. The study area is situated above the treeline from an altitude of 700 m to mountains of 1600 m in Swedish Lapland. We added food (reindeer and moose carcasses) to dens during the winter months, January-April 1985-89. To determine the effect of this extra food on reproduction, we made inventories at both food-manipulated dens and control dens. These inventories of dens took place during July so we could check not only if dens were occupied, but also whether a litter was born and assess the number of cubs appearing outside the den. (3) The proportion of occupied dens in the experimental group was significantly higher than in the control group. The number of cubs at weaning in the food-manipulated dens was also higher than in control dens in each year. However, no effect on litter size was found. (4) From these results we conclude that the larger number of cubs produced in dens with extra winter food shows that reproduction under present dietary poor conditions was limited by available food. Many canid species show this close relation between reproduction and food availability, with pregnancy rates and litter sizes declining with the abundance of the main food.

  • 29.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Börjesson, Patrik
    Stockholm University, Faculty of Science, Department of Zoology.
    Brandberg, K.
    Stable isotope analysis of harbour porpoises and their prey from the Baltic and Kattegat/Skagerrak Seas2006In: Marine Biology Research, ISSN 1745-1000, E-ISSN 1745-1019, Vol. 2, no 6, p. 411-419Article in journal (Refereed)
    Abstract [en]

    The by-caught harbour porpoises in commercial fisheries have raised concerns over their conservation status in the Baltic region. One important aspect for management purposes is porpoise movements within the region. We measured stable isotopes in cod, herring and hagfish, species that are important prey for harbour porpoises in the Baltic region. Bone collagen in fish from the marine Kattegat/Skagerrak was significantly enriched in C-13 compared with collagen in fish from the brackish Baltic Sea. However, despite the isotopic variation seen in their prey, we found no difference in C-13 in harbour porpoise collagen from the two areas. In fact, only eight of 24 porpoises had isotope signatures corresponding to those estimated for the diet in the area where they were caught. Our general conclusion is that porpoises move between the Baltic and Kattegat/Skagerrak Seas. Future studies are needed to evaluate the magnitude of these movements.

  • 30.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hjernquist, B.
    A Rapid Summer Decline in a Mountain Hare Population on an Island1984In: Acta Theriologica, ISSN 0001-7051, E-ISSN 2190-3743, Vol. 29, no 1-10, p. 63-75Article in journal (Refereed)
  • 31.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pehrson, A.
    Factors Influencing Winter Food Choice by Mountain Hares (Lepus-Timidus L) on Swedish Coastal Islands1987In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 65, no 9, p. 2163-2167Article in journal (Refereed)
    Abstract [en]

    In mainland areas, mountain hares seem unable to survive on a single browse species. However, mountain hares on islands off the west coast of Sweden rely almost entirely on a plain heather diet during winter. Herein, we give as a possible explanation for this phenomenon that the high concentration of sodium in the heather in the coastal areas can buffer the high sodium excretion otherwise observed in hares feeding on heather under experimental conditions. Furthermore, hares selected heather with the highest nitrogen and phosphorus contents. We argue that the pattern of food choice exhibited by the hares in the coastal area is to be expected in homogenous habitats where hares rely on one dominant food species. In heterogenous habitats, the possibility of food selection on a nutritional level is to a considerable extent overridden by effects of digestibility and concentration of secondary compounds in the different food plants available.

  • 32.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, M.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bjärvall, A.
    Ericson, M.
    From, J.
    Noren, E.
    Dynamics of the Arctic Fox Population in Sweden1995In: Annales Zoologici Fennici, Vol. 32, no 1, p. 55-68Article in journal (Refereed)
    Abstract [en]

    Arctic fox populations fluctuate widely with the abundance of prey, i.e. lemmings and voles (Arvicolinae). We have investigated the patterns and mechanisms of these fluctuations in arctic fox numbers through den inventories during 20 years (1974-1993) in Sweden. Time series analyses confirmed a four-year cyclicity in both arctic fox numbers and litter size. However, the different geographical regions were not in synchrony. The fox population in the southern parts of the distribution range has shown regular peaks during the whole period, whereas those in the northern and middle parts of Sweden have declined since 1982. In the northernmost county, also litter sizes have decreased. These differences coincided with an absence of vole and lemming peaks in the north. Experimental feeding confirmed that food availability had a direct impact on breeding success and litter size, thereby limiting the population. We conclude that the total number of arctic foxes in Sweden in 1994 is as low as 40-80 animals.

  • 33.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Erlinge, S.
    Predator-prey relationships: Arctic foxes and lemmings1999In: Journal of Animal Ecology, Vol. 68, no 1, p. 34-49Article in journal (Refereed)
    Abstract [en]

    1. The number of breeding dens and litter sizes of arctic foxes Alopex lagopus were recorded and the diet of the foxes was analysed during a ship-based expedition to 17 sites along the Siberian north coast. At the same time the cyclic dynamics of coexisting lemming species were examined. 2. The diet of arctic foxes was dominated by the Siberian lemming Lemmus sibiricus (on one site the Norwegian lemming L. lemmus), followed by the collared lemming Dicrostonyx torquatus. 3. The examined Lemmus sibiricus populations were in different phases of the lemming cycle as determined by age profiles and population densities. 4. The numerical response of arctic foxes to varying densities of Lemmus had a time lag of 1 year, producing a pattern of limit cycles in lemming-arctic fox interactions, Arctic fox litter sizes showed no time lag, but a linear relation to Lemmus densities. We found no evidence for a numerical response to population density changes in. Dicrostonyx. 5. The functional or dietary response of arctic foxes followed a type II curve for Lemmus, but a type III response curve for Dicrostonyx. 6. Arctic foxes act as resident specialist for Lemmus and may increase the amplitude and period of their population cycles. For Dicrostonyx, on the other hand, arctic foxes act as generalists which suggests a capacity to dampen oscillations.

  • 34.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Lundberg, Håkan
    Stockholm University, Faculty of Science, Department of Zoology.
    Geographical and temporal patterns of lemming population dynamics in Fennoscandia2001In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 24, no 3, p. 298-308Article in journal (Refereed)
    Abstract [en]

    There is a long-lasting debate in ecology on cyclicity, synchrony and time lags of lemming population fluctuations. We have analysed 137 yr of previously published population data on the Norwegian lemming Lemmus lemmus in ten geographic regions of Fennoscandia. The dominating pattern was synchronous 4-yr cycles. There was no support for the hypothesis of a north-south gradient in cycle length. However. we found periods of prolonged interruptions in the cyclicity, which were more common in northern areas. Wa found a high degree of synchrony between regions. with only a weak relationship to distance, The observed pattern in lemming population dynamics was more consistent with effects from extrinsic factors, such as climate. than intrinsic factors. such as dispersal.

  • 35.
    Ankar, Sven
    Stockholm University.
    The soft bottom ecosystem of the northern Baltic proper with special reference to the macrofauna1977Doctoral thesis, comprehensive summary (Other academic)
  • 36. Antonopoulou, Efthimia
    et al.
    Swanson, Penny
    Borg, Bertil
    Stockholm University, Faculty of Science, Department of Zoology.
    Effects of aromatase inhibitors and different doses of testosterone on gonadotropins in one year old male Atlantic salmon (Salmo salar).2009In: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, ISSN 1531-4332, Vol. 153, no 4, p. 408-16Article in journal (Refereed)
    Abstract [en]

    The effects of different doses of testosterone (T), the aromatase inhibitors 1,4,6-androstatriene-3,17-dione (ATD) and 4-hydroxy-4-androstene-3,17-dione (4OH), and the combined treatment of T and ATD on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) at the onset of puberty in juvenile Atlantic salmon males were investigated. T always increased pituitary LH. Also, ATD increased pituitary LH, though to a lesser extent than T. However, ATD combined with T diminished pituitary LH levels compared to T alone, indicating an aromatase-dependent positive feedback of T on LH in immature males. 4OH, which was less effective than ATD as an aromatase inhibitor, increased LH content. ATD treatment resulted in increased pituitary FSH levels, similar to those of mature controls. Positive effects of ATD on plasma FSH were found, indicating the presence of an aromatase-dependent negative feedback. The 4OH effects on FSH levels were inconsistent. T exerted both positive and negative effects on pituitary FSH and testes growth, depending on dose and season, with the positive effects being more pronounced with the low doses and the negative effects with the high doses. The treatment of T combined with ATD did not affect the positive effect of T alone on pituitary and plasma FSH, indicating the presence of an aromatase-independent positive feedback on FSH. There was a positive correlation between FSH and gonadosomatic index, especially during summer when gonadal development occurs.

  • 37.
    Araújo, Priscila
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Universidade Federal de Minas Gerais, Brazil.
    de Almeida Caetano, Carolina
    Schlindwein, Clemens
    Alves-Dos-Santos, Isabel
    Mota, Theo
    Body size and the architecture of the visual system in crepuscular and diurnal bees2023In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 138, no 3, p. 328-340Article in journal (Refereed)
    Abstract [en]

    Crepuscular bees have larger compound eyes, ommatidia and ocelli than diurnal bees. These visual adaptations allow these bees to forage during twilight. While the sizes of visual organs are positively correlated with body size in diurnal bees, this relationship is as yet unclear in crepuscular bees. Here we measured the sizes of the ocellus; compound eyes; ommatidial density; and dorsal, frontal and ventral facets of 11 phylogenetically related bee species with different temporal patterns. We tested whether and how each of these visual attributes is correlated with body size and/or temporal pattern. Except for ommatidial density and size of the frontal ommatidia, which are similar in crepuscular bees of different sizes, we found that all other visual variables in diurnal and crepuscular bees are correlated with both body size and temporal pattern. The lower variability in ommatidial density among crepuscular bees suggests that their eyes operate on the threshold between light sensitivity and visual acuity. Furthermore, similar frontal ommatidial sizes in bees of different sizes indicate that this eye region is under higher evolutionary pressure in small than in large crepuscular bees to ensure light sensitivity. Finally, those crepuscular bees from different families convergently share the same visual characteristics.

  • 38.
    Arnbom, Tom
    Stockholm University, Faculty of Science.
    Maternal investment in male and female offspring in the southern elephant seal1994Doctoral thesis, comprehensive summary (Other academic)
  • 39.
    Aronsson, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Colour and pattern similarity in mimicry: evidence for a hierarchical discriminative learning of different components2012In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 84, no 4, p. 881-887Article in journal (Refereed)
    Abstract [en]

    Many aposematic species combine their bright colours with a black pattern that produces internal contrasts. Studies have shown that birds often pay attention to some parts of a signalling pattern and disregard others, which could be of importance in Batesian mimicry, where a palatable species copies the visual appearance of a distasteful model in order to deceive predators. We used domestic chicks, Gallus gallus domesticus, and artificial prey signals to investigate whether predators use different warning colour components for discrimination depending on the degree of information about prey quality they convey. This study supports earlier findings of the importance of colour for discrimination among prey but also provides evidence that other less associable signal properties such as internal patterning, when holding valuable discriminatory information, can be used to assess prey quality in a hierarchical manner. The results also suggest that, in certain circumstances, the presence of a palatable mimic can have positive effects on learning, resulting in 'super-Mullerian' effects. We propose that the degree of selection for perfect mimicry may be dependent on the proportion of well-educated predators in the population.

  • 40.
    Aronsson, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Evidence of signaling benefits to contrasting internal color boundaries in warning coloration2013In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 24, no 2, p. 349-354Article in journal (Refereed)
    Abstract [en]

    It has been suggested that the common existence of regular patterning in aposematic prey animals makes them stand out from the background, improving detection and recognition. Another suggestion is that internal patterns could have a similar positive effect on predator aversion learning as prey-to-background contrast. We used wild caught blue tits (Cyanistes caeruleus) and artificial prey signals to investigate if internal color boundaries, pattern regularity and pattern symmetry affect learning. Birds in different treatments were trained, on a complex background, to discriminate between artificial prey with different nonrewarding color stimuli with a black pattern and rewarding stimuli without a black pattern, followed by a generalization test. This study provides evidence of learning benefits to internally contrasting patterns as the striped prey stimuli were learned faster than the unstriped. Also, we found no beneficial effects of pattern regularity and symmetry. The birds generalized more between prey with different black patterns than to the profitable prey, suggesting that color is of foremost importance. The generalization test also showed a greater avoidance of striped than that of unstriped prey, suggesting some attention on patterns. Thus, internal patterning may affect signal salience and in some circumstances benefit prey due to both a faster avoidance learning and generalization behavior.

  • 41.
    Aronsson, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Importance of internal pattern contrast and contrast against the background in aposematic signals.2009In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 20, no 6, p. 1356-1362Article in journal (Refereed)
    Abstract [en]

    Aposematic color patterns that signal prey unprofitability are suggested to work best when there is high contrast within the animal color pattern or between the animal and its background. Studies show that prey contrast against the background increases the signal efficiency. This has occasionally been extended to also explain the presence of internal patterns. We used domestic chicks, Gallus gallus domesticus, to investigate the relative importance for avoidance learning of within-prey pattern contrast and prey contrast against the background. In a series of trials, birds were first trained to avoid artificially made aposematic mealworms that were plain red or red with black stripes, and to discriminate them from palatable brown mealworms, on either a red or a brown background. Second, we investigated how the birds generalized between striped and nonstriped prey. The chicks showed faster avoidance learning when the basic color of the aposematic prey (red) contrasted with the background color (brown). However, there was no similar effect of internal pattern contrast. The generalization test showed a complete generalization between the nonstriped and the striped prey. We conclude that contrasting internal patterns do not necessarily affect predator avoidance learning the same way as shown for prey-to-background contrast in aposematic prey.

  • 42.
    Audehm, Uwe
    et al.
    Institute of Zoophysiology, University of Bonn, Germany.
    Trube, Anke
    Institute of Zoophysiology, University of Bonn, Germany.
    Dircksen, Heinrich
    Institute of Zoophysiology, University of Bonn, Germany.
    Patterns and projections of crustacean cardioactive-peptide-immunoreactive neurons of the terminal ganglion of crayfish.1993In: Cell and Tissue Research, ISSN 0302-766X, E-ISSN 1432-0878, Vol. 272, no 3, p. 473-485Article in journal (Refereed)
    Abstract [en]

    Three distinct clusters of crustacean cardioactive-peptide-immunoreactive neurones occur in the terminal abdominal ganglion of the crayfish species Orconectes limosus, Astacus leptodactylus, Astacus astacus and Procambarus clarkii, as revealed by immunocytochemistry of whole-mount preparations and sections. They exhibit similar topology and projection patterns in all four studied species. An anterior ventral lateral and a posterior lateral cluster contain one small, strongly stained perikaryon and two large, less intensely stained perikarya, each showing contralateral projections. A posterior medial lateral cluster of up to six cells also contains these two types of perikarya. Whereas the small type perikarya belong to putative interneurones, the large type perikarya give rise to extensive neurohaemal plexuses in perineural sheaths of the third roots of the fifth abdominal ganglia, the connectives, the dorsal telson nerves, the ganglion itself, its roots and arteriolar supply. Thin fibres from these plexuses reach newly discovered putative neurohaemal areas around the hindgut and anus via the intestinal and the anal nerves, and directly innervate the phasic telson musculature. A comparison with earlier investigations of motoneurones and segmentation indicates that these three cell groups containing putative neurosecretory neurones may be members of at least three neuromeres in this ganglion. Crustacean cardioactive peptide released from these neurones may participate in the neurohumoral and modulatory control of different neuronal and muscle targets, thereby exceeding its previously established hindgut and heart excitatory effects.

  • 43.
    Audusseau, Hélène
    Stockholm University, Faculty of Science, Department of Zoology.
    Effect of climate and land use on niche utilization and distribution of nettle-feeding  butterflies2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Anthropogenic changes in climate and land use are causing a dramatic erosion of biodiversity. To understand this erosion, and predict future transformations of biodiversity, we need to understand better species’ response to these changes at different spatial and temporal scales. Modeling studies have identified correlations between physical parameters of the environment and species’ distribution at large spatial scales. However, this does not accurately characterize the response of a specific species, since this does not account for the constraints arising from the biology of the species. This thesis shall combine knowledge on the biology of species obtained from laboratory experiments with modeling studies. This will allow us (i) to identify life history traits and biotic interactions that influence species’ adaptive potential, and hence, explain possible differences in species’ distribution, and (ii) to consider, not only the ecological but also the evolutionary aspects of species’ response to changes. This integrative approach is likely to improve our predictions on species’ population dynamic in a changing environment.

    I focus on a community of butterflies in Sweden (Vanessa cardui, Polygonia c-album, Aglais urticae, Aglais io, Araschnia levana) that feeds on the stinging nettle (Urtica dioica). The available knowledge on the biology of these species and their short life cycles, which allow investigations of their response to changes on a short-time scale, make them a good system to study. Among three of these species, I showed great differences in organisms’ response to variation in food nutrient content. This is a potentially important finding considering the increased use of chemical fertilizers. These differences are to a large extent explained by differences among species in their degree of host plant specialization and voltinism (paper II). Thus, life history traits determine the response of species to environmental changes, but are themselves likely to evolve in response to such changes. Climate change, for instance, may alter the phenological synchrony between plant-feeding insects and their host plants, making it necessary for the insects to evolve their host plant range in order to ensure the availability of resources during larval development (paper I & III). The biology of a species, including biotic interactions, helps to explain the observed shift in a species’ distribution and environmental niche that result from climate change. I have shown that the recent establishment of A. levana in southern Sweden has modified the niche of the resident species, A. urticae and A. io (Paper IV). Niche partitioning in this community is likely mediated by parasite-driven apparent competition.

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  • 44.
    Axén, Annkristin H.
    Stockholm University, Faculty of Science, Department of Zoology.
    Behaviour of Lycaenid butterfly larvae in their mutualistic interactions with ants2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Interspecific mutualism often involves partners trading different kinds of services. The cost and benefits of the trade may differ from one interaction to the next, or fluctuate over time in a single interaction, due to factors both internal and external to the mutualism itself. Aspects of partner quality, such as a partner's ability to provide services and its need for the services obtained in return, are likely to be particularly important. As a consequence of such variation, one might expect strategies of adjusting investments to the characteristics of the partner and to other circumstances, in a way that increases the benefit received and/or decreases the investment necessary to obtain the benefit. Lycaenid butterfly larvae often interact mutualistically with ants, which they reward with nutritious secretions in return for being protected from parasitoids and predators. The larvae also have other means of influencing ants, such as a pair of eversible tentacular organs, which emit volatile substances that attract and alert ants. Both participants in the interaction can readily modify their mutualistic investments over very short periods of time. My aim in this thesis has been to investigate strategies individual larvae could use to change the cost-benefit relationship of the interaction in a way that increases their returns. For this purpose I have manipulated factors that might influence the outcome of the mutualism for lycaenids and observed their response, both as tentacle signalling and in the form of investment in secretions. Examples of factors I have investigated are the level of ant attendance, the need for protection, and the species of the attending ants. I have also investigated the effect of group size and companion quality in a gregarious lycaenid species. I have found that larvae react to such changed circumstances by varying their behaviour, either acting to increase the number of attending ants when better protection is likely to be needed or reducing the costly secretion when adequate protection is already available. My overall conclusion is that lycaenid larvae have a series of adaptations that serve to efficiently regulate the number of protecting ants and that much of the variability I have observed can be interpreted in this way.

  • 45. Baba, Yuki G.
    et al.
    Walters, Richard J.
    Stockholm University, Faculty of Science, Department of Zoology.
    Miyashita, Tadashi
    Host-dependent differences in prey acquisition between populations of a kleptoparasitic spider Argyrodes kumadai (Araneae: Theridiidae)2007In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 32, no 1, p. 38-44Article in journal (Refereed)
    Abstract [en]

    1. A kleptoparasitic spider, Argyrodes kumadai, is known to use phylogenetically unrelated host species in different regions - Cyrtophora moluccensis (Araneidae) in south-west Japan and Agelena silvatica (Agelenidae) in north-east Japan. The work reported here examined whether differences in host characters affect prey acquisition of A. kumadai. 2. Field surveys showed that prey-biomass capture rate of Argyrodes was significantly higher in populations parasitising Cyrtophora than in populations parasitising Agelena. Although Argyrodes appeared to catch fewer prey within Cyrtophora webs, they were able to feed upon substantially larger prey. 3. Differences in prey-biomass capture rate were found to reflect differences in host traits rather than regional differences in potential prey availability. Individuals in populations parasitising Cyrtophora were observed to acquire prey via a number of foraging tactics that included stealing wrapped food bundles, feeding upon prey remains and, in the case of large prey items, feeding together with the host. In contrast, individuals in populations parasitising Agelena were only ever observed to feed upon small prey items ignored by its host. 4. This variability in prey acquisition between kleptoparasite populations reflected different opportunities for feeding within their respective host webs - opportunities that were primarily determined by the foraging behaviour of the host. One key trait associated with host foraging behaviour was host-web structure, namely the presence/absence of a retreat.

  • 46.
    Barth, Lukas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Are Norwegian lemmings Lemmus lemmus avoided by arctic Alopex lagopus or red foxes Vulpes vulpes? A feeding experiment2000In: Wildlife Biology, Vol. 6, no 2, p. 101-109Article in journal (Refereed)
    Abstract [en]

    Arctic fox Alopex lagopus and red fox Vulpes vulpes are close relatives with similar niche demands in the Holarctic. Where they are sympatric, they compete for territories, dens and food. Seat analyses from Fennoscandia have shown different proportions of lemmings and voles in the diets of the two fox species suggesting food partitioning. However, it was not clear if this was due to different food preferences or distinct habitat use. Since the arctic fox is an endangered species in Fennoscandia, it is important to know whether the superior, north spreading red fox can oust it from the tundra habitat, or if food specialisation may prevent displacement. In a feeding experiment at the Lycksele Zoo in northern Sweden, we compared the food preferences of two arctic and two red foxes. Our results show that the four individuals responded similarly to a variety of food items, and particularly that the two species were not distinct in their food preferences concerning lemmings and voles. However, the foxes had considerable individual predilections. Therefore, in the wild, the unequal proportions of lemmings and voles found in seats may reflect different habitat use for hunting.

  • 47. Bartholomée, Océane
    et al.
    Dwyer, Ciara
    Tichit, Pierre
    Stockholm University, Faculty of Science, Department of Zoology. Lund University, Sweden.
    Caplat, Paul
    Baird, Emily
    Stockholm University, Faculty of Science, Department of Zoology.
    Smith, Henrik G.
    Shining a light on species coexistence: visual traits drive bumblebee communities2023In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 290, no 1996, article id 20222548Article in journal (Refereed)
    Abstract [en]

    Local coexistence of bees has been explained by flower resource partitioning, but coexisting bumblebee species often have strongly overlapping diets. We investigated if light microhabitat niche separation, underpinned by visual traits, could serve as an alternative mechanism underlying local coexistence of bumblebee species. To this end, we focused on a homogeneous flower resource—bilberry—in a heterogeneous light environment—hemi-boreal forests. We found that bumblebee communities segregated along a gradient of light intensity. The community-weighted mean of the eye parameter—a metric measuring the compromise between light sensitivity and visual resolution—decreased with light intensity, showing a higher investment in light sensitivity of communities observed in darker conditions. This pattern was consistent at the species level. In general, species with higher eye parameter (larger investment in light sensitivity) foraged in dimmer light than those with a lower eye parameter (higher investment in visual resolution). Moreover, species realized niche optimum was linearly related to their eye parameter. These results suggest microhabitat niche partitioning to be a potential mechanism underpinning bumblebee species coexistence. This study highlights the importance of considering sensory traits when studying pollinator habitat use and their ability to cope with changing environments. 

  • 48.
    Bartosiewicz, Laszlo
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Osteoarchaeological Research Laboratory.
    Lisk, Elicia
    Mammalian Remains2018In: Quedem Reports, E-ISSN 0793-4289, Vol. 10, p. 83-117Article, book review (Refereed)
  • 49. Baur, Julian
    et al.
    Zwoinska, Martyna K.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Koppik, Mareike
    Snook, Rhonda R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Berger, David
    Heat stress reveals a fertility debt owing to postcopulatory sexual selection2023In: Evolution Letters, E-ISSN 2056-3744Article in journal (Refereed)
    Abstract [en]

    Climates are changing rapidly, demanding equally rapid adaptation of natural populations. Whether sexual selection can aid such adaptation is under debate; while sexual selection should promote adaptation when individuals with high mating success are also best adapted to their local surroundings, the expression of sexually selected traits can incur costs. Here we asked what the demographic consequences of such costs may be once climates change to become harsher and the strength of natural selection increases. We first adopted a classic life history theory framework, incorporating a trade-off between reproduction and maintenance, and applied it to the male germline to generate formalized predictions for how an evolutionary history of strong postcopulatory sexual selection (sperm competition) may affect male fertility under acute adult heat stress. We then tested these predictions by assessing the thermal sensitivity of fertility (TSF) in replicated lineages of seed beetles maintained for 68 generations under three alternative mating regimes manipulating the opportunity for sexual and natural selection. In line with the theoretical predictions, we find that males evolving under strong sexual selection suffer from increased TSF. Interestingly, females from the regime under strong sexual selection, who experienced relaxed selection on their own reproductive effort, had high fertility in benign settings but suffered increased TSF, like their brothers. This implies that female fertility and TSF evolved through genetic correlation with reproductive traits sexually selected in males. Paternal but not maternal heat stress reduced offspring fertility with no evidence for adaptive transgenerational plasticity among heat-exposed offspring, indicating that the observed effects may compound over generations. Our results suggest that trade-offs between fertility and traits increasing success in postcopulatory sexual selection can be revealed in harsh environments. This can put polyandrous species under immediate risk during extreme heat waves expected under future climate change.

  • 50.
    Becedas, Luisa
    Stockholm University, Faculty of Science.
    Xenobiotic-conjugating enzymes in rat ovary: hormonal regulation of UDP-glucuronosyltransferase and glutathione transferase and release of mutagenic metabolites by granulosa cells1997Doctoral thesis, comprehensive summary (Other academic)
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