Wild LA, Chenoweth EM, Mueter FJ, Straley JM. Evidence for dietary time series in layers of cetacean skin using stable carbon and nitrogen isotope ratios.
RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018;
32:1425-1438. [PMID:
29777550 PMCID:
PMC6097889 DOI:
10.1002/rcm.8168]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 05/05/2018] [Accepted: 05/06/2018] [Indexed: 05/22/2023]
Abstract
RATIONALE
Stable isotope analysis integrates diet information over a time period specific to the type of tissue sampled. For metabolically active skin of free-ranging cetaceans, cells are generated at the basal layer of the skin and migrate outward until they eventually slough off, suggesting potential for a dietary time series.
METHODS
Skin samples from cetaceans were analyzed using continuous-flow elemental analyzer isotope ratio mass spectrometry. We used ANOVAs to compare the variability of δ13 C and δ15 N values within and among layers and columns ("cores") of the skin of a fin, humpback, and sperm whale. We then used mixed-effects models to analyze isotopic variability among layers of 28 sperm whale skin samples, over the course of a season and among years.
RESULTS
We found layer to be a significant predictor of δ13 C values in the sperm whale's skin, and δ15 N values in the humpback whale's skin. There was no evidence for significant differences in δ15 N or δ13 C values among cores for any species. Mixed-effects models selected layer and day of the year as significant predictors of δ13 C and δ15 N values in sperm whale skin across individuals sampled during the summer months in the Gulf of Alaska.
CONCLUSIONS
These results suggest that skin samples from cetaceans may be subsampled to reflect diet during a narrower time period; specifically different layers of skin may contain a dietary time series. This underscores the importance of selecting an appropriate portion of skin to analyze based on the species and objectives of the study.
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