Biology subjects

Hazlerigg, D.

Publications and source records attributed to Hazlerigg, D..

4 recordsLinked to original sources

bioRxiv2024

Impact of three light smoltification regimes on performance and genetic parameters of traits in Atlantic salmon

2800 Atlantic salmon pre-smolts (50 g on average, the offspring of 53 sires and 100 dams) were individually tagged with PIT-tags and distributed among six circular 1200L tanks with approximately 450 fish per tank. Fish in duplicated tanks were put on three different light regimes, i.e. six weeks on either 8L:16D, 12L:12D or 24L:0D followed by six weeks on 24L:0D. One week prior to their transfer as 1+ smolt to a net cage in the sea in June 2021 their body weight, length, subjectively scored smolt status and fin damage were recorded. Recording of animal traits (body weight, wounds, fin damage, snout damage) were also performed in November 2021 and in April 2022. During the light regimes, fish on the two short day regimes had slower growth compared to fish on continuous light. However, after four (November 2021) and ten (April 2022) months in the sea the effect of light regime on fish size was not significantly different from zero (P>0.05). The fish on the 24L:0D regime showed increased mortality from day two after sea transfer with an accumulated recorded mortality of 8.9% during the two first months while it was only 1.0% and 0.7% for the 12L:12D and the 8L:16D fish, respectively. However, from the third until ten months in the sea recorded mortality was very similar for fish on the three light regimes. The effect of light regime on the recorded welfare traits (fin and snout damage and runts) was not significantly different from zero. For traits measured prior to seawater transfer the difference between fish that survived and those that died during the first two months in the sea were largest in the 24L:0D group indicating a positive effect of the short-day regimes also on the general smolt synchronization (i.e., group level uniformity). Moderate heritability estimates were found for the external smolt indicator traits condition factor, smolt status score and skin silveriness, as well as for snout damage, wounds, runts and body weight, but low estimates fin damage. For survival in the sea heritability on the liability scale was 0.09 after four months in the sea and 0.22 from five to ten months in the sea. The estimated genetic correlations between the same trait of the three different light regimes were moderate to high and thus unimportant genotype by light regime interaction. The genetic correlation of body in June 2021 with survival after two months in the sea was high (0.96), but not significantly different from zero with survival after four months in the sea and survival from five to ten months in the sea. Genetic correlations of survival with the other traits recorded in June 2021, November 2021 and April 2022 were low to medium in magnitude and not significantly different from zero. Therefore, for genetic improvement of survival in the seawater period direct selection for increased survival and growth during the first months is probably a better strategy than to perform indirect selection for smolt indicator traits.

genetics↗

bioRxiv2023

c-fos induction in the choroid plexus, tanycytes and pars tuberalis is an early indicator of spontaneous arousal from torpor in a deep hibernator

Hibernation is an extreme state of seasonal energy conservation, reducing metabolic rate to as little as 1% of the active state. During the hibernation season, many species of hibernating mammals cycle repeatedly between the active (aroused) and hibernating (torpid) states (T-A cycling), using brown adipose tissue (BAT) to drive cyclical rewarming. The regulatory mechanisms controlling this process remain undefined but are presumed to involve thermoregulatory centres in the hypothalamus. Here, we use the golden hamster (Mesocricetus auratus), and high-resolution monitoring of BAT, core body temperature (Tb), and ventilation rate, to sample at precisely defined phases of the T-A cycle. Using c-fos as a marker of cellular activity we show that although the dorso-medial hypothalamus (DMH) is active during torpor entry, neither it nor the pre-optic area (POA) show any significant changes during the earliest stages of spontaneous arousal. Contrastingly, in 3 non-neuronal sites previously linked to control of metabolic physiology over seasonal and daily timescales, the choroid plexus (CP), pars tuberalis (PT) and third ventricle tanycytes, peak c-fos expression is seen at arousal initiation. We suggest that through their sensitivity to factors in the blood or cerebrospinal fluid (CSF), these sites may mediate metabolic feedback-based initiation of the spontaneous arousal process.

physiology↗

bioRxiv2023

Circadian coupling of mitochondria in a deep-diving mammal

Regulation of mitochondrial oxidative phosphorylation is essential to match energy supply to changing cellular energy demands, and to cope with periods of hypoxia. Recent work implicates the circadian molecular clock in control of mitochondrial function and hypoxia sensing. Since diving mammals experience intermittent episodes of severe hypoxia, with diel patterning in dive depth and duration, it is interesting to consider circadian - mitochondrial interaction in this group. Here we demonstrate that the hooded seal (Cystophora cristata), a deep diving Arctic pinniped, shows strong daily patterning of diving behaviour in the wild. Cultures of hooded seal skin fibroblasts exhibit robust circadian oscillation of the core clock genes per2 and arntl. In liver tissue collected from captive hooded seals, expression of arntl was some 4-fold higher in the middle of night than in the middle of the day. To explore the clock-mitochondria relationship, we measured the mitochondrial oxygen consumption in synchronized hooded seal skin fibroblasts and found a circadian variation in mitochondrial activity, with higher coupling efficiency of complex I coinciding with the trough of arntl expression. These results open the way for further studies of circadian - hypoxia interactions in pinnipeds during diving. SUMMARY STATEMENTA functional clockwork and circadian variation in mitochondrial complex I efficiency is demonstrated in skin fibroblasts from the deep diving hooded seal.

physiology↗

bioRxiv2021

Genome-wide reconstruction of rediploidization following autopolyploidizationacross one hundred million years of salmonid evolution

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 (ohnologues) to diverge genetically and functionally. Our understanding of autopolyploid rediploidization has been informed by a WGD event ancestral to salmonid fishes, where large genomic regions are characterized by temporally delayed rediploidization, allowing lineage-specific ohnologue sequence divergence in the major salmonid clades. Here, we investigate the long-term outcomes of autopolyploid rediploidization at genome-wide resolution, exploiting a recent explosion of salmonid genome assemblies, including a new genome sequence for the huchen (Hucho hucho). We developed a genome alignment approach to capture duplicated regions across multiple species, allowing us to create 121,864 phylogenetic trees describing ohnologue divergence across salmonid evolution. Using molecular clock analysis, we show that 61% of the ancestral salmonid genome experienced an initial wave of rediploidization in the late Cretaceous (85-106 Mya). This was followed by a period of relative genomic stasis lasting 17-39 My, where much of the genome remained in a tetraploid state. A second rediploidization wave began in the early Eocene and proceeded alongside species diversification, generating predictable patterns of lineage-specific ohnologue divergence, scaling in complexity with the number of speciation events. Finally, using gene set enrichment, gene expression, and codon-based selection analyses, we provide insights into potential functional outcomes of delayed rediploidization. Overall, this study enhances our understanding of delayed autopolyploid rediploidization and has broad implications for future studies of WGD events.

genomics↗