This work was conducted with the support of the Cooperative Research Program for Agriculture Science &#38; Technology Development (Project title: Livestock productivity change analysis with climate change, Project No. PJ012771), Rural Development Administration, Republic of Korea. Also, this study was supported by a grant (No. PJ01344604) from the Animal Nutrition &#38; Physiology Team, National Institute of Animal Science, RDA, Seoul, Republic of Korea. The authors gratefully acknowledge Persian Gesture CEO Mohammad Hassan Salmanzadeh and his team, who provided fish from the three sturgeon species examined in this study.

The following experimental procedures and methods were approved by the Animal Welfare and Ethics Authority of Kangwon National University, Chuncheon, Republic of Korea.
1. Fin collection
<ol>
	<li>Capture the sturgeon gently using a net to minimize injury and stress.</li>
	<li>Rinse the fish carefully with fresh water and then wipe the body surface with an absorbent towel prior to euthanasia.</li>
	<li>Hit the head of the fish using a plastic hammer such that the fish is stunned or loses consciousness. Remove the head using a knife.</li>
	<li>Measure the body weight (g) and length (cm).</li>
	<li>After euthanasia, collect fin samples by cutting as close as the body as possible using sterilized surgical scissors. 
	NOTE: Individual, non-recycled absorbent towels must be used for each fish. Descriptive statistics for the species used in this study were as follows: beluga sturgeon (H. huso): age = 18 &#177; 2.1 months, body weight = 2,700 &#177; 300 g, and body length = 55 &#177; 5 cm; Siberian sturgeon (A. baerii): age = 9.6 &#177; 2.4 months, body weight = 1,750 &#177; 250 g, and body length = 45 &#177; 5 cm; sevruga sturgeon (A. stellatus): age = 14 &#177; 1.3 months, body weight = 1,000 &#177; 100 g, and body length = 65 &#177; 5 cm.</li>
</ol>
2. Fin preparation for cortisol extraction
<ol>
	<li>Place the fin samples (one sample per tissue: ~3 g) on laboratory weighing paper (107 mm &#215; 210 mm) and dry at room temperature for a few days until dry.</li>
	<li>Wrap samples in sheets of aluminum foil, place in labeled plastic bags, and transfer to the laboratory.</li>
	<li>Store samples in a refrigerator for further use, including washing, cortisol extraction, drying, and ELISA analysis (Figure 2).</li>
</ol>
3. Fin cortisol analysis
<ol>
	<li>Calibrate the digital analytical scale (accuracy: 0.0001) and weigh out 300 &#177; 10 mg samples with weighing paper on the scale pan.</li>
	<li>Wash the samples.
	<ol>
		<li>Transfer each sample into a 15 L conical polypropylene tube. Add 3 mL of isopropanol to each tube using a 5,000 &#181;L single-channel pipette.</li>
		<li>Rotate the tubes at 80&#160;rpm for 2.5 min to wash out cortisol and remove any potential external contamination. Repeat this procedure twice.</li>
		<li>Air-dry the washed samples at room temperature (22-28 &#176;C) for 7 days.</li>
		<li>Repeat the washing procedure using ultrapure water as the washing agent.</li>
	</ol>
	</li>
	<li>Extract the jawbone from the body tissue using bone-cutting forceps. Apply steps 1.5-3.2.4 to the jawbone samples.</li>
	<li>Weigh out (75 &#177; 5 mg) dried fin or jawbone samples and grind using a bead beater at 50 Hz for 32 min.
	<ol>
		<li>Deliver 1.5 mL of methanol into each tube containing powdered fin or jawbone using a 1000 &#181;L pipette. Place the samples on a tube rotator at slow rotation (40 rpm) for 18 h at room temperature to extract cortisol with continuous mixing.</li>
	</ol>
	</li>
	<li>Following cortisol extraction, centrifuge the samples at 9,500 x g for 10 min at room temperature. After centrifugation, collect the top organic layer containing cortisol (1 mL) from each sample and place it into a separate 1.5 mL microcentrifuge tube.
	<ol>
		<li>Dry the samples by incubation at 38 &#176;C to evaporate the methanol. Keep the extracted cortisol samples under a fume hood overnight to allow methanol to dissipate. 
		NOTE: The cortisol-containing layer is usually yellowish in color.</li>
	</ol>
	</li>
</ol>
4. Fin cortisol detection
<ol>
	<li>Thaw the dried fin or jawbone samples at room temperature for 1.5 h prior to using the ELISA kit.</li>
	<li>Add 400 &#181;L of phosphate buffer, vortex, and centrifuge at 1,500 x g for 15 min.</li>
	<li>Run each sample (25 &#181;L) in duplicate to improve assay accuracy and reliability. Remove any data outside the standard curve as outliers.</li>
	<li>Set a microplate reader to 450 nm, then set to &#181;g dL-1 and read the optical density of the plate.
	<ol>
		<li>Use the microplate software with a four-parameter non-linear regression curve fit. Convert the cortisol levels of the samples obtained from the software into pg mg-1 using the following equation: 
		F = 10,000E (A/B) (C/D), 
		where F = the final value of the fin cortisol level in (pg mg-1), E = the volume (mL) of the assay buffer used to reconstitute the dried extract, A = the concentration (&#181;g dL-1) provided by the assay output, B = the weight (mg) of the fin subjected to extraction, C = the volume (mL) of methanol added to the powdered fin, and D = the volume (mL) of methanol recovered from the extract and subsequently dried down3.</li>
	</ol>
	</li>
</ol>
5.Statistical analysis
<ol>
	<li>Divide each sample into two sub-samples prior to the washing procedure and then run in duplicate during the ELISA kit assay (2 &#215; 2 = 4 observations per sample) to improve the power of the test and reliability of the results.</li>
	<li>Compare the effects of the two washing solvents and their interactions by applying the general linear model (GLM) procedure in the SAS software environment to the measurement data18.</li>
	<li>Test differences between means using Tukey&#39;s test at a significance level of p &#60; 0.05. Accept 0.05 &#60; p &#60; 0.10 as evidence of a tendency rather than as a significant difference.</li>
</ol>

<ol>
	<li>Meyer, J. S., Novak, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hair+cortisol:+a+novel+biomarker+of+hypothalamic-pituitary-+adrenocortical+activity.">Hair cortisol: a novel biomarker of hypothalamic-pituitary- adrenocortical activity.</a> Endocrinology. 153, 4120-4127 (2012).</li><li>Ghassemi Nejad, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cortisol+study:+facial+hair+and+nails.">A cortisol study: facial hair and nails.</a> Journal of Steroids Hormonal Sciences. 7, 1-5 (2016).</li><li>Meyer, J. S., Novak, M. A., Hamel, A., Rosenberg, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+and+analysis+of+cortisol+from+human+and+monkey+hair.">Extraction and analysis of cortisol from human and monkey hair.</a> Journal of Visualized Experiments. (83), e50882 (2014).</li><li>Davenport, M. D., Tiefenbacher, S., Lutz, C. K., Novak, M. A., Meyer, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+endogenous+cortisol+concentrations+in+the+hair+of+rhesus+macaques.">Analysis of endogenous cortisol concentrations in the hair of rhesus macaques.</a> General and Comparative Endocrinology. 147, 255-261 (2006).</li><li>Ghassemi Nejad, J., Ataallahi, M., Park, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methodological+validation+of+measuring+Hanwoo+hair+cortisol+concentration+using+bead+beater+and+surgical+scissors.">Methodological validation of measuring Hanwoo hair cortisol concentration using bead beater and surgical scissors.</a> Journal of Animal Science and Technology. 61, 41-46 (2019).</li><li>Ghassemi Nejad, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wool+cortisol+is+a+better+indicator+of+stress+than+blood+cortisol+in+ewes+exposed+to+heat+stress+and+water+restriction.">Wool cortisol is a better indicator of stress than blood cortisol in ewes exposed to heat stress and water restriction.</a> Animal. 8, 128-132 (2014).</li><li>Brossa, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cortisol in skin mucus and scales as a measure of fish stress and habitat quality. Ph.D. dissertation. , (2018).</li><li>Carbajal, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cortisol+detection+in+fish+scales+by+enzyme+immunoassay:+biochemical+and+methodological+validation.">Cortisol detection in fish scales by enzyme immunoassay: biochemical and methodological validation.</a> Journal of Applied Ichthyology. 34, 1-4 (2018).</li><li>Bertotto, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+matrices+for+cortisol+measurement+in+fish.">Alternative matrices for cortisol measurement in fish.</a> Aquaculture Research. 41, 1261-1267 (2010).</li><li>Ghassemi Nejad, J., Jeong, C., Shahsavarani, H., Sung, I. K., Lee, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embedded+dental+cortisol+content:+a+pilot+study.">Embedded dental cortisol content: a pilot study.</a> Endocrinology &amp; Metabolic Syndrome. 5, 240 (2016).</li><li>Pankhurst, N. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+endocrinology+of+stress+in+fish:+an+environmental+perspective.">The endocrinology of stress in fish: an environmental perspective.</a> General and Comparative Endocrinology. 170, 265-275 (2011).</li><li>Ghassemi Nejad, J., Kim, W. B., Lee, B. H., Sung, K. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coat+and+hair+color:+hair+cortisol+and+serotonin+levels+in+lactating+Holstein+cows+under+heat+stress+conditions.">Coat and hair color: hair cortisol and serotonin levels in lactating Holstein cows under heat stress conditions.</a> Animal Science Journal. 88, 190-194 (2017).</li><li>Baker, M. R., Gobush, K. S., Vynne, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review+of+factors+influencing+stress+hormones+in+fish+and+wildlife.">Review of factors influencing stress hormones in fish and wildlife.</a> Journal of Nature Conservation. 21, 309-318 (2013).</li><li>Aerts, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scales+tell+a+story+on+the+stress+history+of+fish.">Scales tell a story on the stress history of fish.</a> PLoS One. 10, e0123411 (2015).</li><li>Heimb&#252;rge, S., Kanitz, E., Otten, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+hair+cortisol+for+the+assessment+of+stress+in+animals.">The use of hair cortisol for the assessment of stress in animals.</a> General and Comparative Endocrinology. , 10-17 (2019).</li><li>Ghassemi Nejad, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+hair+cortisol+concentrations+from+various+body+sites+and+serum+cortisol+in+Holstein+lactating+cows+and+heifers+during+thermal+comfort+zone.">Comparing hair cortisol concentrations from various body sites and serum cortisol in Holstein lactating cows and heifers during thermal comfort zone.</a> Journal of Veterinary Behavior: Clinical and Application Research. 30, 92-95 (2019).</li><li>Bussy, U., Wassink, L., Scribner, K. T., Li, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+cortisol+in+lake+sturgeon+(Acipenser+fulvescens)+eggs+by+liquid+chromatography+tandem+mass+spectrometry.">Determination of cortisol in lake sturgeon (Acipenser fulvescens) eggs by liquid chromatography tandem mass spectrometry.</a> Journal of Chromatography B. 1040, 162-168 (2017).</li><li>SAS. 1999. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SAS. User's Guide (Version 8.01 Edition). , (1999).</li><li>Barton, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress+in+fishes:+a+diversity+of+responses+with+particular+reference+to+changes+in+circulating+corticosteroids.">Stress in fishes: a diversity of responses with particular reference to changes in circulating corticosteroids.</a> Integrative and Comparative Biology. 42, 517-525 (2002).</li><li>Ghassemi Nejad, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+hair+and+blood+cortisol+in+sheep+and+dairy+cattle+using+RIA+and+ELISA+assay:+a+comparison.">Measuring hair and blood cortisol in sheep and dairy cattle using RIA and ELISA assay: a comparison.</a> Biological Rhythm Research. Accepted. , (2019).</li></ol>

The authors have no conflicts of interest to disclose.

Sturgeon is sometimes called a &#34;living fossil&#34; because it has exhibited few adaptations throughout past millennia. The sturgeon genus Acipenser contains 27 species that produce caviar; however, three species (beluga, baerii, and sevruga) produce most of the global caviar supply. Sturgeon are vulnerable to over-fishing and interference in their natural habitat and are therefore more critically endangered than any other group of species. Sturgeon belong to the oldest group of living vertebrates, which has existed for 150 million years. Acipenser species mature and grow slowly; some (e.g., H. huso) can live for 100 years and exceed 2,000 kg in weight. Sturgeon are cartilaginous fish without scales, and are characterized by five rows of large, bony plates called scutes and tactile barbels located at the front of the mouth (Figure 1). Physiological differences between these species and other fish include decreased plasma (corticosteroid) responses to environmental stressors. Our fin cortisol measurements provide evidence that the sturgeon jawbone accumulates cortisol in proportion to circulating concentrations.
Fish display numerous responses to physical, chemical, and perceived stressors. These reactions are well known as adaptive mechanisms that allow the fish to cope with environmental disturbances and maintain a homeostatic state. If a stressor is sufficiently prolonged or serious that the fish is unable to regain homeostasis using its natural responses, then the fish may experience adverse effects, endangering its overall health and/or life19. The sex of sturgeon can be determined from around 2 years of age. Therefore, to determine whether cortisol levels and sturgeon sex are correlated, it is necessary to document long-term cortisol accumulation in fins and jawbones (as a new approach and alternative matrix) of sturgeon. This study is the first to report fin and jawbone cortisol levels in sturgeon.
The role of a cortisol wash solvent is to remove external cortisol sources from the skin mucus9. Aerts et al.14 used distilled water to remove external cortisol contamination from fish skin; in previous studies2,5,12,17, we compared the effects of using isopropanol and water as a solvent to examine hair cortisol content. The effects of wash solvent can vary among samples due to differences in the properties of sturgeon eggs13, skin15, fins, and jawbones. Brossa7 reported that cortisol level in scales of goldfish (Carassius auratus) remained constant when isopropanol was used as the solvent regardless of the number of washes, whereas cortisol levels varied when water was used. Our results showed that washing solvent had no effect on jaw cortisol levels. Differences between these studies include the number of washes, shaking vs. vortexing, isopropanol purity, and importantly, sensitivity or resistance of scales/skin to external liquid penetration. Ghassemi Nejad et al.20 demonstrated that the application of different assays such as RIA and ELISA can lead to differences in output. Steroids are more soluble in lower molecular mass alcohols (e.g., methanol) than in alcohols of higher molecular weight such as isopropanol4. Methanol extraction denatures protein by breaking non-covalent bonds, thus allowing hair cortisol release. Methanol also modifies hormone structure by breaking non-covalent bonds, resulting in the release of cortisol from tissues. To effectively homogenize sturgeon fins and jawbones prior to methanol extraction, a bead beater can be used to efficiently break down the tissue structure. This procedure requires time to completely grind fin and jawbone samples; therefore, the process must be repeated to ensure complete pulverization and homogenization prior to cortisol extraction. Slow rotation for 18 h permits the gradual removal of cortisol by washing.
As suggested in previous studies of mammal hair4,5,6, external or internal sources of cortisol content in fins and jaws, other than blood, should not be neglected. Although this study was not specifically designed to investigate how cortisol diffuses from blood to fins or jaws, it highlights the need to expand our knowledge of this process to better interpret fluctuations in cortisol from these matrices. The properties of fins and jawbones differ from those of scales and skin. Bussy et al.17 quantified cortisol levels in lake sturgeon (A. fulvescens) eggs to investigate environmental effects on maternal physiological condition and egg quality. They used methyl tert-butylether (MTBE), ethyl acetate (AcOEt) MTBE, and diethyl ether (Et2O) as washing solvents and concluded that ethyl acetate was the best extraction solvent in terms of recovery and matrix effect. In the present study, isopropanol removed greater amounts of external cortisol from skin mucus during washing, leading to a slight overestimation of cortisol from sturgeon fins, which must be carefully considered when interpreting extraction results. It is possible that isopropanol was able to wash out the skin of the fin, as has been reported in a previous study7. Isopropanol is known to penetrate hair follicles and fish scales4,7. The results of the present study indicate that the choice of solvent had no significant effect on cortisol levels, suggesting that cortisol extraction may be more difficult in some parts of the fin than in others using ultrapure water; in such cases, isopropanol may be used as an alternative.
This study demonstrated the applicability of the jawbone as a novel matrix for the reliable indication of stress in sturgeon. H. huso jawbone cortisol values were similar to those extracted from fins of the same species; future studies should confirm this result among different species, ages, and sexes via correlation analysis. A low number of fish was used in the current study due to the high cost of sturgeon; we attempted to overcome this limitation by testing each sample twice and also duplicating methanol extraction for the ELISA. Using quadruple multiplication could increase the power of the test to cover the low number of samples.
We conclude that the type of washing solvent moderately affected cortisol extraction from fins, but not jaws, of sturgeon. Before generalizing the conclusion of this study and to validate these results, further research using different species and solvents should be conducted. The present work provides evidence that the sturgeon jawbone can be applied as an alternative matrix in future studies using cortisol as an index of stress in sturgeon. The suitability of ELISA for fin and jawbone cortisol measurement was also demonstrated in the present study. Future research should focus on two aspects: 1) determining the correlation between cortisol levels in jawbones and those in fins of sturgeon and 2) harvesting matrix samples for cortisol measurement from older fish and their caviar to determine long-term stress levels in different sturgeon species over the lifespan.

Cortisol is a reliable indicator of animal stress. Cortisol extraction provides a valid framework for researchers to monitor stress levels and general patterns in stressors. For example, previous studies have conducted methodological validation of hair cortisol measurements using various methods in humans1,2, monkeys3,4, cattle5, sheep6, and goldfish7,8. In fish species, cortisol measurements in matrices such as scales, skin mucus, feces, and blood9 have been shown to provide information on fish health. When blood sampling is problematic or scales are lacking, alternative matrices for cortisol extraction are needed. In fish, alternative matrices can include the jawbone, a hard tissue&#160;similar to the human tooth10.
The development of new matrices and validated techniques to determine fish stress levels is of particular interest to the caviar industry, where sturgeon can experience prolonged exposure to environmental stress factors11. The sex of sturgeon cannot be determined before 2 years of age, and sturgeon do not have scales. Because cortisol gradually accumulates in solid matrices during the growth stage2,7,12, long-term cortisol accumulation data from hard matrices such as fins and jawbones could provide insight into stress levels at different growth stages. In contrast, blood cortisol levels provide a snapshot of stress levels at the time of death and cannot accurately represent stress during long-term rearing conditions13,14. With increasing competition in the caviar market, new approaches to improve stress conditions for the production of healthier eggs among sturgeon species during long-term rearing (8-12 years or longer) are an increasingly important area of research. Due to the high cost of sturgeon, harvested samples are extremely costly ($8,000-15,000 per mature fish depending on species and growth stage), a limiting factor for research projects. However, the development of an appropriate technique for cortisol extraction from sturgeon fins and jawbones could be usefully applied both to fish farming systems and in wild fish to improve the quality and harvest of sturgeon eggs for both consumption and conservation.
As well as providing reliable results6, the selection of an appropriate cortisol extraction technique is of critical importance to ensure that other compounds present in the matrix during sample preparation do not confound the output, which might lead to inconsistent results. It is equally important to determine whether fin and jawbone cortisol levels are influenced by hormone levels in the surrounding water. Heimb&#252;rge et al.15 suggested that a number of factors may influence cortisol levels including age, sex, pregnancy, season, color12, and body region from which cortisol is extracted16. However, little information is available on the effects of washing solvents on cortisol extraction in fish body matrices8, and none on these effects in sturgeon, except for sturgeon eggs17.
Although analyzing baseline cortisol levels from the fins and jawbones of sturgeon requires that the fish be euthanized, this approach does not entail the invasive techniques required for blood sampling in live sturgeon. Fin and jawbone samples are easily collected, and extraction from these tissues can be performed rapidly. Similarly, hormone extraction and analysis are straightforward and require little specialized equipment.
In this study, we present a new and easily applied technique for the extraction, washing, and determination of cortisol from fish fins and jawbones, with the aim of determining whether cortisol levels measured from these matrices can be reliably used as stress indicators. The advantages of this technique include an easy and non-invasive8 approach, less data variation, and reliable output1,6,8,17; the technique is applicable to fish species without scales such as sturgeon. The technique requires slaughter of the fish, selection of appropriate washing solvents2,4, proper grinding of samples3,5, professional enzyme-linked immunosorbent assay (ELISA) application5,7, and extensive knowledge of the incorporation of cortisol sources into solid matrices6.
We applied two different washing solvents (ultrapure water and isopropanol) to obtain basal cortisol levels in fins from three sturgeon species: beluga (Huso huso), Siberian (Acipenser baerii), and sevruga (A. stellatus), under standard environmental conditions for each species. Jawbones of H. huso were also used to evaluate stress in sturgeon. This is the first study to measure cortisol levels in sturgeon jawbones. The results of this study will provide comparative cortisol data for sturgeon species in the early growth stage (~1 year) prior to sex determination.

<table border="0" cellpadding="0" cellspacing="0" style="width:654px;" width="653">
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			<td height="21" style="height:21px;">Micro-centrifuge capable of 1500 x g</td>
			<td style="width:222px;">Labo Gene</td>
			<td style="width:137px;">&#160;9.900.900.729</td>
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		<tr height="21">
			<td height="21" style="height:21px;">Mini vortex mixer</td>
			<td>LMS</td>
			<td>VTX-3000L&#160;</td>
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		<tr height="21">
			<td height="21" style="height:21px;">Lotte aluminum foil roll&#160;</td>
			<td>Lotte Aluminum</td>
			<td>B0722X5FK5</td>
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			<td height="21" style="height:21px;">Digital scale</td>
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			<td height="21" style="height:21px;">Ultrapure water</td>
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			<td height="21" style="height:21px;">Pipette tips</td>
			<td>Neptune Scientific</td>
			<td>REF 2100.N</td>
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			<td height="21" style="height:21px;">Large fish net</td>
			<td>Pond H2O</td>
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			<td height="21" style="height:21px;">Salivary cortisol kit</td>
			<td>Salimetrics</td>
			<td>1-3002-4</td>
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			<td height="19" style="height:20px;">Bone cutting forceps</td>
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			<td height="42" style="height:42px;width:295px;">Precision multichannel pipette to deliver 50 &#956;L and 200 &#956;L</td>
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cortisol extraction from sturgeon fin and jawbone matrices

The aims of this study were to develop a technique for the extraction of cortisol from sturgeon fins using two washing solvents (water and isopropanol) and quantify any differences in fin cortisol levels among three main sturgeon species. Fins were harvested from 19 sacrificed sturgeons including seven beluga (Huso huso), seven Siberian (Acipenser baerii), and five sevruga (A. stellatus). The sturgeons were raised in Iranian farms for 2 years (2017-2018), and cortisol extraction analysis was conducted in South Korea (January-February 2019). Jawbones from five H. huso were also used for cortisol extraction. Data were analyzed using the general linear model (GLM) procedure in the SAS environment. The intra- and inter-assay coefficients of variation were 14.15 and 7.70, respectively. Briefly, the cortisol extraction technique involved washing the samples (300 &#177; 10 mg) with 3 mL of solvent (ultrapure water and isopropanol) twice, rotation at 80&#160;rpm for 2.5 min, air-drying the washed samples at room temperature (22-28 &#176;C) for 7 days, further drying the samples using a bead beater at 50 Hz for 32 min and grinding them into powder, applying 1.5 mL methanol to the dried powder (75 &#177; 5 mg), and slow rotation (40 rpm) for 18 h at room temperature with continuous mixing. Following extraction, samples were centrifuged (9,500 x g for 10 min), and 1 mL supernatant was transferred into a new microcentrifuge tube (1.5 mL), incubated at 38 &#176;C to evaporate the methanol, and analyzed via enzyme-linked immunosorbent assay (ELISA). No differences were observed in fin cortisol levels among species or in fin and jawbone cortisol levels between washing solvents. The results of this study demonstrate that the sturgeon jawbone matrix is a promising alternative stress indicator to solid matrices.

The presented fin cortisol extraction technique was developed and confirmed in this study using three sturgeon species. Cortisol levels obtained using ultrapure water and isopropanol as washing solvents were compared (Figure 2). Cortisol from H. huso jawbones was examined to determine whether sturgeon jawbones might be used as an alternative matrix to fins. The effects of washing solvent, sturgeon species, and their interaction are shown in Table 1. Cortisol levels tended to be higher in fin samples washed with isopropanol than in those washed with water (p = 0.089). There were no significant differences in fin cortisol levels (p = 0.525) among sturgeon species. There was no significant interaction between washing solvents and sturgeon species (p = 0.947). Washing solvent had no significant effect on cortisol level in H. huso sturgeon (p = 0.45) (Table 2). Intra-assay and inter-assay coefficients of variation were 14.15 and 7.70, respectively. The data showed high similarity among fins of the three sturgeon species (Table 1) and in H. huso jawbones (Table 2). We did not investigate correlations between cortisol levels in jawbones and those in fins of different sturgeon species because we obtained jawbone samples only from H. huso. These relationships should be explored in a future study.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59961/59961fig1.jpg" /> 
Figure 1. (A) Photograph of Huso huso sturgeon (10 years old). (B) Morphological characteristics of sturgeon. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59961/59961fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59961/59961fig2v2.jpg" /> 
Figure 2. Infographic of fin cortisol analysis5,6 performed in the laboratory. All photographs presented in the infographic abstract were taken in the laboratory. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59961/59961fig2v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table>
	<tbody>
		<tr>
			<td colspan="4">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Sturgeon species (SS)</td>
			<td></td>
			<td colspan="3">Washing solvent (WS)</td>
			<td colspan="3">P-value</td>
		</tr>
		<tr>
			<td></td>
			<td>Huso huso</td>
			<td>Acipenser baerii</td>
			<td>Acipenser stellatus</td>
			<td>SEM</td>
			<td>Water</td>
			<td>Isopropanol</td>
			<td>SEM</td>
			<td>SS</td>
			<td>WS</td>
			<td>SS&#215;WS</td>
		</tr>
		<tr>
			<td rowspan="2">Cortisol (pg mg-1)</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3.46</td>
			<td>2.85</td>
			<td>3.34</td>
			<td>0.41</td>
			<td>2.86</td>
			<td>3.69</td>
			<td>0.33</td>
			<td>0.52</td>
			<td>0.08</td>
			<td>0.95</td>
		</tr>
	</tbody>
</table>
Table 1. Fin cortisol levels in three sturgeon species obtained using two different washing solvents.
<table>
	<tbody>
		<tr>
			<td></td>
			<td colspan="2">Washing solvent (WS)</td>
			<td>SEM</td>
			<td>P-value</td>
		</tr>
		<tr>
			<td></td>
			<td>Water</td>
			<td>Isopropanol</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cortisol (pg mg-1)</td>
			<td>1.11</td>
			<td>1.43</td>
			<td>0.31</td>
			<td>0.45</td>
		</tr>
	</tbody>
</table>
Table 2. Jawbone cortisol levels in beluga sturgeon (Huso huso) using two different washing solvents.

Watch this Scientific Journal Video about Cortisol Extraction from Sturgeon Fin and Jawbone Matrices at JoVE.com

Cortisol Extraction from Sturgeon Fin and Jawbone Matrices

In this study, we present a protocol for cortisol extraction from the fin and jawbone of sturgeon species. Fin and jawbone cortisol levels were further examined by comparing two washing solvents followed by ELISA assays. This study piloted the feasibility of jawbone cortisol as a novel stress indicator.

The aims of this study were to develop a technique for the extraction of cortisol from sturgeon fins using two washing solvents (water and isopropanol) ...

cortisol-extraction-from-sturgeon-fin-and-jawbone-matrices

Nanyang Technological University

Research

JoVE Journal

Environment

8.1K Views.  Kangwon National University. In this study, we present a protocol for cortisol extraction from the fin and jawbone of sturgeon species. Fin and jawbone cortisol levels were further examined by comparing two washing solvents followed by ELISA assays. This study piloted the feasibility of jawbone cortisol as a novel stress indicator.

Video: Cortisol Extraction from Sturgeon Fin and Jawbone Matrices

Helminth Collection and Identification from Wildlife

Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are &#34;roundworms&#34; (nematodes), &#34;thorny-headed worms&#34; (acanthocephalans), &#34;flukes&#34; (trematodes), and &#34;tapeworms&#34; (cestodes). The optimum method for collecting helminths is to examine a host that has been dead less than 4-6 hr since most helminths will still be alive. A thorough necropsy should be conducted and all major organs examined. Organs are washed over a 106 &#956;m sieve under running water and contents examined under a stereo microscope. All helminths are counted and a representative number are fixed (either in 70% ethanol, 10% buffered formalin, or alcohol-formalin-acetic acid). For species identification, helminths are either cleared in lactophenol (nematodes and small acanthocephalans) or stained (trematodes, cestodes, and large acanthocephalans) using Harris&#39; hematoxylin or Semichon&#39;s carmine. Helminths are keyed to species by examining different structures (e.g. male spicules in nematodes or the rostellum in cestodes). The protocols outlined here can be applied to any vertebrate animal. They require some expertise on recognizing the different organs and being able to differentiate helminths from other tissue debris or gut contents. Collection, preservation, and staining are straightforward techniques that require minimal equipment and reagents. Taxonomic identification, especially to species, can be very time consuming and might require the submission of specimens to an expert or DNA analysis.

Wild animals are commonly parasitized by a wide range of helminths.&#160; The four major types of helminths are &#8220;roundworms&#8221; (nematodes), &#8220;thorny-headed worms&#8221; (acanthocephalans), &#8220;flukes&#8221; (trematodes), and &#8220;tapeworms&#8221; (cestodes).&#160; Here we describe how helminths are collected from a vertebrate animal and how they are preserved and taxonomically identified.&#160;

Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are &#34;roundworms&#34; (nematodes), ...

Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions

We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is built and can be transported to a temporary work space close to field sampling site(s) to facilitate rapid analysis. Cores are extruded into a portable glove bag, where they are sectioned and each 1-3 cm thick section (depending on core diameter) is sealed into 50 ml centrifuge tubes. Pore waters are separated with centrifugation outside of the glove bag and then returned to the glove bag for separation from the sediment. These extracted pore water samples can be analyzed immediately. Immediate analyses of redox sensitive species, such as sulfide, iron speciation, and arsenic speciation indicate that oxidation of pore waters is minimal; some samples show approximately 100% of the reduced species, e.g. 100% Fe(II) with no detectable Fe(III). Both sediment and pore water samples can be preserved to maintain chemical species for further analysis upon return to the laboratory.

A protocol for sectioning sediment cores and extracting pore waters under anoxic conditions in order to permit analysis of redox sensitive species in both solids and fluids is presented.

We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is ...

A Simple Method for Automated Solid Phase Extraction of Water Samples for Immunological Analysis of Small Pollutants

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and enables to perform rapid, automated and simple SPE. The pre-concentrated solution is compatible with analysis by immunoassay, with a low organic solvent content. A method is described for the extraction and pre-concentration of natural hormone 17&#946;-estradiol in 100 ml water samples. Reverse phase SPE is performed with octadecyl-silica sorbent and elution is done with 200 &#181;l of methanol 50% v/v. Eluent is diluted by adding di-water to lower the amount of methanol. After preparing manually the SPE column, the overall procedure is performed automatically within 1 hr. At the end of the process, estradiol concentration is measured by using a commercial enzyme-linked immune-sorbent assay (ELISA). 100-fold pre-concentration is achieved and the methanol content in only 10% v/v. Full recoveries of the molecule are achieved with 1 ng/L spiked de-ionized and synthetic sea water samples.

A protocol for the extraction and pre-concentration of estradiol from water samples by using an automated and miniaturized system is presented.

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and ...

Simultaneous DNA-RNA Extraction from Coastal Sediments and Quantification of 16S rRNA Genes and Transcripts by Real-time PCR

Real Time Polymerase Chain Reaction also known as quantitative PCR (q-PCR) is a widely used tool in microbial ecology to quantify gene abundances of taxonomic and functional groups in environmental samples. Used in combination with a reverse transcriptase reaction (RT-q-PCR), it can also be employed to quantify gene transcripts. q-PCR makes use of highly sensitive fluorescent detection chemistries that allow quantification of PCR amplicons during the exponential phase of the reaction. Therefore, the biases associated with &#39;end-point&#39; PCR detected in the plateau phase of the PCR reaction are avoided. A protocol to quantify bacterial 16S rRNA genes and transcripts from coastal sediments via real-time PCR is provided. First, a method for the co-extraction of DNA and RNA from coastal sediments, including the additional steps required for the preparation of DNA-free RNA, is outlined. Second, a step-by-step guide for the quantification of 16S rRNA genes and transcripts from the extracted nucleic acids via q-PCR and RT-q-PCR is outlined. This includes details for the construction of DNA and RNA standard curves. Key considerations for the use of RT-q-PCR assays in microbial ecology are included.

A protocol to quantify bacterial 16S rRNA genes and transcripts from coastal sediments via real-time PCR is provided. The methodology includes the co-extraction of DNA and RNA; preparation of DNA-free RNA; and 16S rRNA gene and transcript quantification via RT-q-PCR, including standard curve construction.

Real Time Polymerase Chain Reaction also known as quantitative PCR (q-PCR) is a widely used tool in microbial ecology to quantify gene abundances of ...

Alternative Method of Removing Otoliths from Sturgeon

Extracting the otoliths (ear bones) from fish that have very thick skulls can be difficult and very time consuming. The common practice of making a transverse vertical incision on the top of the skull with a hand or electrical saw may damage the otolith if not performed correctly. Sturgeons (Acipenseridae) are one family in particular that have a very large and thick skull. A new laboratory method entering the brain cavity from the ventral side of the fish to expose the otoliths was easier than other otolith extraction methods found in the literature. Methods reviewed in the literature are designed for the field and are more efficient at processing large quantities of fish quickly. However, this new technique was designed to be more suited for a laboratory setting when time is not pressing and successful extraction from each specimen is critical. The success of finding and removing otoliths using this technique is very high and does not compromise the structure in any manner. This alternative technique is applicable to other similar fish species for extracting the otoliths.

The goal of the protocol is to show an effective method to extract the otoliths from sturgeon carcasses.

Extracting the otoliths (ear bones) from fish that have very thick skulls can be difficult and very time consuming. The common practice of making a ...

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about the overall structure of terrestrial microbial communities. PLFA profiling has been extensively used in a range of ecosystems as a biological index of overall soil quality, and as a quantitative indicator of soil response to land management and other environmental stressors.
The standard method presented here outlines four key steps: 1. lipid extraction from soil samples with a single-phase chloroform mixture, 2. fractionation using solid phase extraction columns to isolate phospholipids from other extracted lipids, 3. methanolysis of phospholipids to produce fatty acid methyl esters (FAMEs), and 4. FAME analysis by capillary gas chromatography using a flame ionization detector (GC-FID). Two standards are used, including 1,2-dinonadecanoyl-sn-glycero-3-phosphocholine (PC(19:0/19:0)) to assess the overall recovery of the extraction method, and methyl decanoate (MeC10:0) as an internal standard (ISTD) for the GC analysis.

Phospholipid fatty acids provide information about the structure of soil microbial communities. We present methods for extraction from soil samples with a single-phase chloroform mixture, fractionation of extracted lipids using solid phase extraction columns, and methanolysis to produce fatty acid methyl esters, which are analyzed by capillary gas chromatography.

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about ...

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na2CO3) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca2+). From the six extraction methods used, only the Na2CO3 extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca2+. The Ca2+-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS.

The protocol provides a methodology to solubilize aerobic granular sludge in order to extract alginate-like extracellular polymers (ALE).

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) ...

Use of a Filter Cartridge for Filtration of Water Samples and Extraction of Environmental DNA

Recent studies demonstrated the use of environmental DNA (eDNA) from fishes to be appropriate as a non-invasive monitoring tool. Most of these studies employed disk fiber filters to collect eDNA from water samples, although a number of microbial studies in aquatic environments have employed filter cartridges, because the cartridge has the advantage of accommodating large water volumes and of overall ease of use. Here we provide a protocol for filtration of water samples using the filter cartridge and extraction of eDNA from the filter without having to cut open the housing. The main portions of this protocol consists of 1) filtration of water samples (water volumes &#8804;4 L or &gt;4 L); (2) extraction of DNA on the filter using a roller shaker placed in a preheated incubator; and (3) purification of DNA using a commercial kit. With the use of this and previously-used protocols, we perform metabarcoding analysis of eDNA taken from a huge aquarium tank (7,500 m3) with known species composition, and show the number of detected species per library from the two protocols as the representative results. This protocol has been developed for metabarcoding eDNA from fishes, but is also applicable to eDNA from other organisms.

We describe a protocol for filtration of water samples with a filter cartridge and extraction of environmental DNA (eDNA) without having to cut open the housing to remove the filter. This protocol is developed for metabarcoding eDNA from fishes, but is also applicable to eDNA from other organisms.

Recent studies demonstrated the use of environmental DNA (eDNA) from fishes to be appropriate as a non-invasive monitoring tool. Most of these studies ...

A Lipid Extraction and Analysis Method for Characterizing Soil Microbes in Experiments with Many Samples

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial communities, a relatively precise but effort-intensive technique to assay microbial community composition is phospholipid fatty acid (PLFA) analysis. PLFA was developed to analyze phospholipid biomarkers, which can be used as indicators of microbial biomass and the composition of broad functional groups of fungi and bacteria. It has commonly been used to compare soils under alternative plant communities, ecology, and management regimes. The PLFA method has been shown to be sensitive to detecting shifts in microbial community composition.
An alternative method, fatty acid methyl ester extraction and analysis (MIDI-FA) was developed for rapid extraction of total lipids, without separation of the phospholipid fraction, from pure cultures as a microbial identification technique. This method is rapid but is less suited for soil samples because it lacks an initial step separating soil particles and begins instead with a saponification reaction that likely produces artifacts from the background organic matter in the soil. 
This article describes a method that increases throughput while balancing effort and accuracy for extraction of lipids from the cell membranes of microorganisms for use in characterizing both total lipids and the relative abundance of indicator lipids to determine soil microbial community structure in studies with many samples. The method combines the accuracy achieved through PLFA profiling by extracting and concentrating soil lipids as a first step, and a reduction in effort by saponifying the organic material extracted and processing with the MIDI-FA method as a second step.

The article describes a method that increases throughput while balancing effort and accuracy for extraction of lipids from the cell membranes of microorganisms for use in characterizing both total lipids and the relative abundance of indicator lipids to determine soil microbial community structure in studies with many samples.

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial ...

Extraction of Organochlorine Pesticides from Plastic Pellets and Plastic Type Analysis

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment during manufacturing and transport. Because of their environmental persistence, they are widely distributed in the oceans and on beaches all over the world. They can act as a vector of potentially toxic organic compounds (e.g., polychlorinated biphenyls) and might consequently negatively affect marine organisms. Their possible impacts along the food chain are not yet well understood. In order to assess the hazards associated with the occurrence of plastic pellets in the marine environment, it is necessary to develop methodologies that allow for rapid determination of associated organic contaminant levels. The present protocol describes the different steps required for sampling resin pellets, analyzing adsorbed organochlorine pesticides (OCPs) and identifying the plastic type. The focus is on the extraction of OCPs from plastic pellets by means of a pressurized fluid extractor (PFE) and on the polymer chemical analysis applying Fourier Transform-InfraRed (FT-IR) spectroscopy. The developed methodology focuses on 11 OCPs and related compounds, including dichlorodiphenyltrichloroethane (DDT) and its two main metabolites, lindane and two production isomers, as well as the two biologically active isomers of technical endosulfan. This protocol constitutes a simple and rapid alternative to existing methodology for evaluating the concentration of organic contaminants adsorbed on plastic pieces.

Microplastics act as vector of potentially toxic organic contaminants with unpredictable effects. This protocol describes an alternative methodology for assessing the levels of organochlorine pesticides adsorbed on plastic pellets and identifying the polymer chemical structure. The focus is on pressurized fluid extraction and attenuated total reflectance Fourier transform infrared spectroscopy.

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment ...