Environmental and Genetic (vgll3) Effects on the Prevalence of Male Maturation Phenotypes in Domesticated Atlantic Salmon

Pre-harvest male maturation is problematic for Atlantic salmon (Salmo salar) farmers and is regulated by the environment and genetics (e.g., vgll3). Five families of all-male salmon parr (produced using YY males crossed with XX females) with different vgll3 genotypes were split between three environmental regimes in January 2018. The “advanced maturation” regime used elevated temperature (16 °C) and continuous light from January 2018 with post-smolt maturation assessed in March 2018. The “extended freshwater” regime used ambient freshwater (1–16 °C) and simulated natural photoperiod (SNP) with post-smolt maturation assessed in November 2018. The “sea transfer” regime used ambient temperatures (1–14 °C) and SNP in freshwater until May 2018 when they were transferred to 9 °C seawater with natural photoperiod for 2.5 years (final mean weight of circa. 14 kg) and assessed for post-smolt maturation, 1 sea-winter (1 SW) maturation, and 2 sea-winter (2 SW) maturation in the autumn (November/December) of 2018, 2019, and 2020, respectively. Post-smolt maturation was highest in the advanced maturation and extended freshwater regimes (39–99% depending on family) and lowest in the sea transfer regime (0–95% depending on family). In the sea transfer regime, maturity incidence increased over time (0–95% post-smolt maturation, 1–100% 1 SW, and 50–90% 2 SW maturation, depending on family). In all regimes, those homozygous for the pre-designated vgll3 “early” maturing allele had the highest incidences of maturation whilst those homozygous for the “late” allele had the lowest. A low percentage of 2 SW phenotypic and genetic females were found (0–5% depending on family), one of which was successfully crossed with an XY male resulting in progeny with an approx. 50/50 sex ratio. These results show (i) post-smolt maturation varies dramatically depending on environment although genetic regulation by vgll3 was as expected, and (ii) crossing YY sperm with XX eggs can result in XX progeny which can themselves produce viable progeny with an equal sex ratio when crossed with an XY male.publishedVersio

A stochastic model to study genetic and metabolic effects on N-linked protein glycosylation

Glycosylation is a vital processing step for a large number of cellular proteins as it critically affects protein stability and solubility as well as protein-protein interactions. As a consequence, glycosylation is a major quality attribute of recombinant proteins in biopharmaceutical applications. However, since glycosylation does not follow a template, but instead involves a complex interplay of various influencing factors in the Golgi, tailoring glycosylation towards certain desired attributes is challenging and usually requires trial-and-error experimentation. Computational modeling offers an intriguing option to understand and rationally engineer the complex reaction network underlying glycosylation. Here we present a computational model that describes N-linked protein glycosylation as a stochastic process. The model successfully recapitulates the biological complexity of glycosylation, but does not require the input of kinetic data. We show how the model can be used to predict the effect of glycosyltransferase knock-outs or overexpression on glycosylation in CHO. In addition, we demonstrate how the model can be linked to flux-balance models of CHO metabolism and use it to predict how cell culture conditions, such as extracellular nutrients, affect glycosylation. Thus, our modeling approach offers a promising tool for engineering glycosylation in both academic and industrial contexts

Effects of laboratory salmon louse infection on osmoregulation, growth and survival in Atlantic salmon

Anadromous Atlantic salmon (Salmo salar) rely on long ocean migrations to build energy stores for maturation and spawning. In seawater, wild Atlantic salmon are threatened by high salmon lice (Lepeophtheirus salmonis) infestation levels resulting from intensive salmonid sea-cage aquaculture. Salmon lice infection can cause a stress response and an osmotic imbalance in the host. The lice infection intensity threshold values for these responses, however, remain to be identified in Atlantic salmon. In order to define this under laboratory conditions, individually tagged F1 wild origin Atlantic post-smolts (40 g) were infected with salmon lice copepodids or left as uninfected controls. Twenty-eight days post infection, infected post-smolts had a mean of 0.38 (range of 0.07–0.9) mobile lice g−1 fish weight. During this period, specific growth rates (SGRs) were lower in infected than control fish (0.4 vs 1.0% day−1). Higher plasma Na+, Cl− and osmolality in infected fish also indicate osmoregulatory impairment. SGR correlated negatively with plasma Na+, Cl−, osmolality and cortisol in the infected, but not in the control group. Infection intensity (lice g−1 fish) correlated positively with mortality rate and plasma Na+, Cl−, osmolality and cortisol and correlated negatively with SGR and condition factor. Calculated lice intensity threshold values for changes in plasma ions were 0.18 lice g−1 for plasma Cl−, and 0.22 lice g−1 for plasma Na+. Moribund infected fish occurred at infection intensities above 0.2 lice g−1, and these fish had extreme plasma Cl−, Na+, osmolality and cortisol levels. There was a positive correlation between plasma cortisol and plasma Na+, Cl− and osmolality in infected fish. This study provides vital information that can be used to define thresholds in the monitoring and conservation of wild Atlantic salmon populations affected by aquaculture-driven salmon lice infestations.publishedVersio

Vertebral deformities in interspecific diploid and triploid salmonid hybrids

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Triploidy effects growth, life history strategies, and bone health in Arctic char (Salvelinus alpinus), but does not impact cataract incidence

Skeletal deformities and ocular cataracts have limited the farm performance of sterile triploid salmonids, but have not been assessed in Arctic char (Salvelinus alpinus). We repeatedly radiographed mixed-sex diploid and triploid char (n = 110/ploidy) of Hammerfest (Norway) origin reared on a natural photoperiod and temperature in freshwater over a 3-year period and assessed cataracts at termination. At the population level, triploids were significantly (p 90% in both ploidy), but severity was low (on average, 0.1). Based on the average wet body mass of immature fish and losses due to sexual maturation and mortality, mono-sex stocks of male triploid fish gave the highest return per 100 juveniles stocked, followed by diploid males, diploid females, and triploid females (87.5, 83.0, 80.8, and 69.3 kg, respectively) at the earliest opportunity to harvest (i.e. when the fish first reached 0.7–1.0 kg). Therefore, all-male triploids may provide benefits to char aquaculture although their skeletal health should be addressed.publishedVersio