affording protection against methylmercury toxicity, little is known regarding the presence of

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

• (see Supplementary Table 1 for additional information on the harvested whales). Comparisons across tissues
• reveal that the skin is the primary reservoir for both compounds. Mean skin concentrations were 17.2 µg/g for
• slightly higher in the kidney (6:1) and lower in the brain (4:1) and blood (3:1) (Supplementary Table 2). As
• a humidity of 70%) compared to belugas (maximum SEN concentrations of 3.26 µg/g, wet weight). Although
• concentrations found in beluga skin (mean 17.2 µg/g) might indicate an important functional role that directs
• mass) in tissues of adult belugas hunted in Quaqtaq, Nunavik, 2018-2019. Sample sizes were n = 14 for skin,
• n = 13 for kidney and liver, n = 12 for muscle, n = 10 for blood and intestine and n = 5 for brain. Different letters
• identify statistically significant differences in mean concentrations across tissues (p < 0.05).
• mushrooms (Pleurotus ostreatus), with mean levels of 528 µg/g and 118 µg/g respectively (wet mass)25.
• detected in fetal blood (Supplementary Table 3). Although SEN and EGT concentrations were notably lower and
• the outer layers was observed in all whales. The lowest mean concentrations were found in the dermis (7.54 µg/g
• 4: dermis (n = 4). Blubber was removed, as indicated by the scissors. Immunofluorescence detection of ETT
• Total body length was recorded to the nearest 0.1 cm from nose to tail (Supplementary Table 1). Samples
• collected included liver (n = 13), kidneys (n = 13), brain (n = 5), muscles (n = 12) and intestines (n = 9). Skin
• samples from all individuals (n = 14) were collected from the dorsal area behind the blowhole, with three
• technical replicates per individual; replicate concentrations were averaged. Blood (n = 14) was collected post-
• was from ThermoFisher (Fair Lawn, NJ). Ammonium formate (99.995%; trace metals basis), dithiothreitol
• (DTT; ≥ 99%), and formic acid (≥ 95%; reagent grade) were purchased from Sigma-Aldrich (St. Louis, MO).
• formaldehyde solution 37%, from laboratory MAT (Quebec, QC) and fluoromount-G mounting medium from
• (n = 4) were cut horisontally into four visually distinct layers (Fig. 4b): the stratum corneum, thin cuticle easily
• operated at 30 °C with a flow rate of 0.4 mL/min. A binary gradient of 0.1% formic acid with 10 mM ammonium
• formate (A) and acetonitrile (B) was used: 0–1.6 min (100% A), 1.6–2 min (linear to 10% A), 2–3.6 min (10%
• A), 3.6–8 min (100% A). The injection volume was 10 µL in full loop mode. The system was coupled to a Xevo
• LOD was established by repeatability (16 replicates) of beluga muscle tissue. Analytical performance
• high-concentration QC and seal muscle and liver for the low-concentration QC (n = 17 for each). For EGT, %
• CV values were below 10% at both concentration levels, showing high instrumental precision. SEN showed
• in a higher % CV (18%). A similar trend was observed for S-methyl-EGT and Se-methyl-SEN: both compounds
• procedure of Bienvenu et al.48. Global matrix effects, depending on the analyte, ranged from 98% to 106%, while
• instrumental matrix effects varied between 96% and 102%, indicating minimal impact on ionisation efficiency
• and quantitative accuracy of the analytes during mass spectrometry analysis. Recovery was above 70% for all
• analytes (Supplementary Table 4).
• heat-fixed (30 min at 37 °C) on a microscope slide. Sections were then fixed in 3% formaldehyde for 15 min at
• RT, permeabilised with 0.1% Tween 20 in PBS for 15 min at RT, and incubated in blocking buffer (5% bovine
• serum albumin, 0.05% Tween 20, and 0.3 M glycine in PBS) for 1 h at RT. They were subsequently incubated with
• ETT/SLC22A4 mouse polyclonal antibody (A01) diluted 1:200, overnight at 4 °C. After washes with 0.1% Tween
• All analyses were performed using R v4.2.250. Concentrations below LOD values were replaced by LOD/2 prior
• (version 3.6.2) and a confidence interval of 95% (Supplementary Table 5a-d). Each ANOVA was performed

Methods (brief)

• liquid chromatography-tandem mass spectrometry to quantify concentrations of selenoneine,
• unattainable samples, this study explores the distribution of key antioxidants in marine mammals. By way of
• samples in ethical agreement with the regional Anguvigaq and their local Anguviait, an Inuit association mandated
• food security in the region11. This unique collaboration with Inuit enabled access to fresh samples from healthy,
• recently harvested animals—an invaluable opportunity for this study, as whale samples for scientific purposes
• study did not involve any live animal experimentation; all samples were obtained post-mortem. The manuscript
• mass) in tissues of adult belugas hunted in Quaqtaq, Nunavik, 2018-2019. Sample sizes were n = 14 for skin,
• to methodological optimisations, including lower LODs and higher precision compared to previous studies.
• skin sample containing as much as 182 µg EGT/g, the highest concentration ever recorded in a marine species.
• a low EGT concentration in a single trout muscle sample (0.07 µg/g); the specific species was not mentioned
• muscle (Fig. 3a–g). It should be noted that we had access to limited brain tissue samples (n = 5) compared to
• and EGT share the same transporter (ETT) for cellular uptake5 (2) accumulate in all sampled tissues, (3) are
• Immunofluorescence labeling of ETT was performed on fresh skin samples collected from four additional
• separate from the rest of the skin, some samples may have lost this layer prior to analysis. To mitigate this,
• triplicate skin sections were sampled from each whale, and mean values were used. Moreover, samples from
• Samples were obtained from 14 beluga whales (Delphinapterus leucas) harvested by Inuit hunters during the
• Total body length was recorded to the nearest 0.1 cm from nose to tail (Supplementary Table 1). Samples
• collected included liver (n = 13), kidneys (n = 13), brain (n = 5), muscles (n = 12) and intestines (n = 9). Skin

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Fish — marine, predatory (tuna, swordfish, shark, king mackerel)
• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Shellfish (shrimp, crab, lobster, clams, oysters, mussels)
• Mercury
• Mercury

Verification notes

• Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
• Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
• Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
• Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
• HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.