English
norskBlar i forfatter "Hazlerigg, David"
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Activity patterns in mammals: Circadian dominance challenged
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-15)The evidence that diel patterns of physiology and behaviour in mammals are governed by circadian ‘clocks’ is based almost entirely on studies of nocturnal rodents. The emergent circadian paradigm, however, neglects the roles of energy metabolism and alimentary function (feeding and digestion) as determinants of activity pattern. The temporal control of activity varies widely across taxa, and ungulates, ... -
Body Temperature and Activity Rhythms Under Different Photoperiods in High Arctic Svalbard ptarmigan (Lagopus muta hyperborea)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-08)Organisms use circadian rhythms to anticipate and exploit daily environmental oscillations. While circadian rhythms are of clear importance for inhabitants of tropic and temperate latitudes, its role for permanent residents of the polar regions is less well understood. The high Arctic Svalbard ptarmigan shows behavioral rhythmicity in presence of light-dark cycles but is arrhythmic during the polar ... -
Circuit-level analysis identifies target genes of sex steroids in ewe seasonal breeding
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-15)Thyroid hormone (TH) and estradiol (E2) direct seasonal switches in ovine reproductive physiology. In sheep, as in other mammals and birds, control of thyrotropin (TSH) production by the pars tuberalis (PT) links photoperiod responsiveness to seasonal breeding. PT-derived TSH governs opposite seasonal patterns of the TH deiodinases Dio2/Dio3 expression in tanycytes of the neighboring medio-basal ... -
Discontinuity in the molecular neuroendocrine response to increasing daylengths in Ile-de-France ewes: Is transient Dio2 induction a key feature of circannual timing?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-24)In mammals, melatonin is responsible for the synchronisation of seasonal cycles to the solar year. Melatonin is secreted by the pineal gland with a profile reflecting the duration of the night and acts via the pituitary pars tuberalis (PT), which in turn modulates hypothalamic thyroid hormone status via seasonal changes in the production of locally‐acting thyrotrophin. Recently, we demonstrated that, ... -
Disrupted seasonal biology impacts health, food security and ecosystems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-10-22)The rhythm of life on earth is shaped by seasonal changes in the environment. Plants and animals show profound annual cycles in physiology, health, morphology, behaviour and demography in response to environmental cues. Seasonal biology impacts ecosystems and agriculture, with consequences for humans and biodiversity. Human populations show robust annual rhythms in health and well-being, and the ... -
Diversified regulation of circadian clock gene expression following whole genome duplication
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-08)Across taxa, circadian control of physiology and behavior arises from cell-autonomous oscillations in gene expression, governed by a networks of so-called ‘clock genes’, collectively forming transcription-translation feedback loops. In modern vertebrates, these networks contain multiple copies of clock gene family members, which arose through whole genome duplication (WGD) events during evolutionary ... -
Effects of photoperiod extension on clock gene and neuropeptide RNA expression in the SCN of the Soay Sheep
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016)In mammals, changing daylength (photoperiod) is the main synchronizer of seasonal functions. The photoperiodic information is transmitted through the retino-hypothalamic tract to the suprachiasmatic nuclei (SCN), site of the master circadian clock. To investigate effects of day length change on the sheep SCN, we used in-situ hybridization to assess the daily temporal organization of expression of ... -
Evidence for circadian-based photoperiodic timekeeping in Svalbard ptarmigan, the northernmost resident bird
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-29)The high Arctic archipelago of Svalbard (74°–81° north) experiences extended periods of uninterrupted daylight in summer and uninterrupted night in winter, apparently relaxing the major driver for the evolution of circadian rhythmicity. Svalbard ptarmigan (<i>Lagopus muta hyperborea</i>) is the only year-round resident terrestrial bird species endemic to the high Arctic and is remarkably adapted to ... -
Genome-Wide Reconstruction of Rediploidization Following Autopolyploidization across One Hundred Million Years of Salmonid Evolution
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-28)The long-term evolutionary impacts of whole-genome duplication (WGD) are strongly influenced by the ensuing rediploidization process. Following autopolyploidization, rediploidization involves a transition from tetraploid to diploid meiotic pairing, allowing duplicated genes (ohnologs) to diverge genetically and functionally. Our understanding of autopolyploid rediploidization has been informed ... -
Gonads or body? Differences in gonadal and somatic photoperiodic growth response in two vole species
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-21)To optimally time reproduction, seasonal mammals use a photoperiodic neuroendocrine system (PNES) that measures photoperiod and subsequently drives reproduction. To adapt to late spring arrival at northern latitudes, a lower photoperiodic sensitivity and therefore a higher critical photoperiod for reproductive onset is necessary in northern species to arrest reproductive development until spring ... -
Immunologic Profiling of the Atlantic Salmon Gill by Single Nuclei Transcriptomics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)Anadromous salmonids begin life adapted to the freshwater environments of their natal streams before a developmental transition, known as smoltification, transforms them into marine-adapted fish. In the wild, smoltification is a photoperiod-regulated process, involving radical remodeling of gill function to cope with the profound osmotic and immunological challenges of seawater (SW) migration. While ... -
Modulation of intestinal growth and differentiation by photoperiod and dietary treatment during smoltification in Atlantic salmon (Salmo salar, L.)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-15)Atlantic salmon undergo smoltification, a process that prepares the fish to enter and thrive in seawater (SW). Several physiological changes occur during smolting, especially in osmoregulatory tissues, the gill, the kidney, and the intestine. Here we characterized the effects on intestinal morphogenesis of two different, commonly used smoltification regimes during the end of the freshwater phase, ... -
Monitoring and analyzing of circadian and ultradian locomotor activity based on Raspberry-Pi
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-15)A new device based on the Raspberry-Pi to monitor the locomotion of Arctic marine invertebrates and to analyze chronobiologic data has been made, tested and deployed. The device uses infrared sensors to monitor and record the locomotor activity of the animals, which is later analyzed. The software package consists of two separate scripts: the first designed to manage the acquisition and the evolution ... -
NFAT5 genes are part of the osmotic regulatory system in Atlantic salmon (Salmo salar)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-18)The anadromous Atlantic salmon utilizes both fresh and salt water (FW and SW) habitats during its life cycle. The parr-smolt transformation (PST) is an important developmental transition from a FW adapted juvenile parr to a SW adapted smolt. Physiological changes in osmoregulatory tissues, particularly the gill, are key in maintaining effective ion regulation during PST. Changes are initiated ... -
Photoperiod and dietary treatment in freshwater modulate the short-term intestinal response to seawater in Atlantic salmon (Salmo salar)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-02)Stimulation and timing of smoltification are essential for successful Atlantic salmon (Salmo salar) aquaculture. This study investigated intestinal responses during dietary and photoperiod manipulation in freshwater (FW) and after a subsequent seven days residence in seawater (SW). “Small” and “large” Atlantic salmon parr (~40 g and ~ 130 g respectively) were treated in FW for 12 weeks and ... -
Photoperiod revisited: is there a critical day length for triggering a complete parr–smolt transformation in Atlantic salmon Salmo salar?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-26)The present study investigated whether there is a critical length of photoperiod needed to stimulate a completed parr–smolt transformation (PST) in Atlantic salmon <i>Salmo salar</i>. In two experiments, <i>S. salar</i> parr of the Norwegian aquaculture strain held on continuous light were exposed to a short photoperiod (6 L:18D) followed by exposure to 8 L:16D, 12 L:12D, 16 L:8D, 20 L:4D and 24 ... -
Photoperiod-dependent developmental reprogramming of the transcriptional response to seawater entry in Atlantic salmon (Salmo salar)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-12)The developmental transition of juvenile salmon from a freshwater resident morph (parr) to a seawater (SW) migratory morph (smolt), known as smoltification, entails a reorganization of gill function to cope with the altered water environment. Recently, we used RNAseq to characterize the breadth of transcriptional change which takes place in the gill in the FW phase of smoltification. This highlighted ... -
Photoperiodic induction without light-mediated circadian entrainment in a High Arctic resident bird
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-21)Organisms use changes in photoperiod to anticipate and exploit favourable conditions in a seasonal environment. While species living at temperate latitudes receive day length information as a year-round input, species living in the Arctic may spend as much as two-thirds of the year without experiencing dawn or dusk. This suggests that specialised mechanisms may be required to maintain seasonal ... -
Phylogenetic Reclassification of Vertebrate Melatonin Receptors To Include Mel1d
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-01)The circadian and seasonal actions of melatonin are mediated by high affinity G-protein coupled receptors (melatonin receptors, MTRs), classified into phylogenetically distinct subtypes based on sequence divergence and pharmacological characteristics. Three vertebrate MTR subtypes are currently described: MT1 (MTNR1A), MT2 (MTNR1B), and Mel1c (MTNR1C / GPR50), which exhibit distinct affinities, ... -
A refined method to monitor arousal from hibernation in the European hamster
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-07)<i>Background</i> - Hibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures. This is achieved through cycles of metabolic depression and reduced body temperature (torpor) and rewarming (arousal). Rewarming from torpor is achieved through the activation of brown adipose tissue (BAT) associated ...
