Determining the appropriate pretreatment procedures and the utility of liver tissue for bulk stable isotope (δ13 C and δ15 N) studies in sharks.
| Title: | Determining the appropriate pretreatment procedures and the utility of liver tissue for bulk stable isotope (δ13 C and δ15 N) studies in sharks. |
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| Authors: | Pahl KB; Department of Integrative Biology, University of Windsor, Windsor, Ontario, Canada.; Yurkowski DJ; Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, Manitoba, Canada.; Wintner SP; KwaZulu-Natal Sharks Board, Maritime Centre of Excellence, Umhlanga Rocks, Umhlanga, South Africa.; Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa.; College of Agriculture, Engineering and Science, School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.; Cliff G; KwaZulu-Natal Sharks Board, Maritime Centre of Excellence, Umhlanga Rocks, Umhlanga, South Africa.; Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa.; College of Agriculture, Engineering and Science, School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.; Dicken ML; KwaZulu-Natal Sharks Board, Maritime Centre of Excellence, Umhlanga Rocks, Umhlanga, South Africa.; Department of Development Studies, School of Economics, Development and Tourism, Nelson Mandela University, Port Elizabeth, South Africa.; College of Agriculture, Engineering and Science, School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.; Hussey NE; Department of Integrative Biology, University of Windsor, Windsor, Ontario, Canada. |
| Source: | Journal of fish biology [J Fish Biol] 2021 Mar; Vol. 98 (3), pp. 829-841. Date of Electronic Publication: 2020 Dec 28. |
| Publication Type: | Journal Article |
| Language: | English |
| Journal Info: | Publisher: Blackwell Publishing Country of Publication: England NLM ID: 0214055 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1095-8649 (Electronic) Linking ISSN: 00221112 NLM ISO Abbreviation: J Fish Biol Subsets: MEDLINE |
| Imprint Name(s): | Publication: 2003- : Oxford, UK : Blackwell Publishing; Original Publication: London, New York, Published for the Fisheries Society of the British Isles by Academic Press. |
| MeSH Terms: | Carbon Isotopes/*analysis ; Chemistry Techniques, Analytical/*veterinary ; Feeding Behavior/*physiology ; Liver/*chemistry ; Nitrogen Isotopes/*analysis; Lipids/chemistry ; Muscles/chemistry ; Sharks/metabolism ; Animals ; Ecosystem ; Species Specificity |
| Abstract: | Stable-isotope analysis (SIA) provides a valuable tool to address complex questions pertaining to elasmobranch ecology. Liver, a metabolically active, high turnover tissue (~166 days for 95% turnover), has the potential to reveal novel insights into recent feeding/movement behaviours of this diverse group. To date, limited work has used this tissue, but ecological application of SIA in liver requires consideration of tissue preparation techniques given the potential for high concentrations of urea and lipid that could bias δ13 C and δ15 N values (i.e., result in artificially lower δ13 C and δ15 N values). Here we investigated the effectiveness of (a) deionized water washing (WW) for urea removal from liver tissue and (b) chloroform-methanol for extraction of lipids from this lipid rich tissue. We then (a) established C:N thresholds for deriving ecologically relevant liver isotopic values given complications of removing all lipid and (b) undertook a preliminary comparison of δ13 C values between tissue pairs (muscle and liver) to test if observed isotopic differences correlated with known movement behaviour. Tests were conducted on four large shark species: the dusky (DUS, Carcharhinus obscurus), sand tiger (RAG, Carcharias taurus), scalloped hammerhead (SCA, Sphyrna lewini) and white shark (GRE, Carcharodon carcharias). There was no significant difference in δ15 N values between lipid-extracted (LE) liver and lipid-extracted/water washed (WW) treatments, however, WW resulted in significant increases in %N, δ13 C and %C. Following lipid extraction (repeated three times), some samples were still biased by lipids. Our species-specific "C:N thresholds" provide a method to derive ecologically viable isotope data given the complexities of this lipid rich tissue (C:N thresholds of 4.0, 3.6, 4.7 and 3.9 for DUS, RAG, SCA and GRE liverLEWW tissue, respectively). The preliminary comparison of C:N threshold corrected liver and muscle δ13 C values corresponded with movement/habitat behaviours for each shark; minor differences in δ13 C values were observed for known regional movements of DUS and RAG (δ13 CDiffs = 0.24 ± 0.99‰ and 0.57 ± 0.38‰, respectively), while SCA and GRE showed greater differences (1.24 ± 0.63‰ and 1.08 ± 0.71‰, respectively) correlated to large-scale movements between temperate/tropical and pelagic/coastal environments. These data provide an approach for the successful application of liver δ13 C and δ15 N values to examine elasmobranch ecology.; (© 2020 Fisheries Society of the British Isles.) |
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| Grant Information: | We thank funding organizations W. Garfield Weston Foundation, NSERC and MEOPAR for D.J.Y. and NSERC Discovery funds for N.E.H. |
| Contributed Indexing: | Keywords: C:N ratio; C:N threshold; elasmobranch; lipid; trophic ecology; urea; δ13C and δ15N |
| Substance Nomenclature: | 0 (Carbon Isotopes); 0 (Lipids); 0 (Nitrogen Isotopes) |
| Entry Date(s): | Date Created: 20201130 Date Completed: 20210426 Latest Revision: 20210426 |
| Update Code: | 20260130 |
| DOI: | 10.1111/jfb.14635 |
| PMID: | 33251592 |
| Database: | MEDLINE |
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