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Shark tooth collagen stable isotopes (δ 15 N and δ 13 C) as ecological proxies
Author(s) -
Shipley Oliver N.,
Henkes Gregory A.,
Gelsleichter James,
Morgan Clark R.,
Schneider Eric V.,
Talwar Brendan S.,
Frisk Michael G.
Publication year - 2021
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.13518
Subject(s) - carcharhinus , stable isotope ratio , biology , δ13c , isotope , isotope analysis , context (archaeology) , chondrichthyes , δ15n , zoology , anatomy , ecology , paleontology , physics , quantum mechanics
The isotopic composition of tooth‐bound collagen has long been used to reconstruct dietary patterns of animals in extant and palaeoecological systems. For sharks that replace teeth rapidly in a conveyor‐like system, stable isotopes of tooth collagen (δ 13 C Teeth & δ 15 N Teeth ) are poorly understood and lacking in ecological context relative to other non‐lethally sampled tissues. This tissue holds promise, because shark jaws may preserve isotopic chronologies from which to infer individual‐level ecological patterns across a range of temporal resolutions. Carbon and nitrogen stable isotope values were measured and compared between extracted tooth collagen and four other non‐lethally sampled tissues of varying isotopic turnover rates: blood plasma, red blood cells, fin and muscle, from eight species of sharks. Individual‐level isotopic variability of shark tooth collagen was evaluated by profiling teeth of different ages across whole jaws for the shortfin mako shark Isurus oxyrinchus and sandbar shark Carcharhinus plumbeus . Measurements of δ 13 C Teeth and δ 15 N Teeth were positively correlated with isotopic values from the four other tissues. Collagen δ 13 C was consistently 13 C‐enriched relative to all other tissues. Patterns for δ 15 N were slightly less uniform; tooth collagen was generally 15 N‐enriched relative to muscle and red blood cells, but congruent with fin and blood plasma (values clustered around a 1:1 relationship). Significant within‐individual variability was observed across whole shortfin mako shark (δ 13 C range = 1.4‰, δ 15 N range = 3.6‰) and sandbar shark (δ 13 C range = 1.2‰–2.4‰, δ 15 N range = 1.7‰–2.4‰) jaws, which trended with tooth age. We conclude that amino acid composition and associated patterns of isotopic fractionation result in predictable isotopic offsets between tissues. Within‐individual variability of tooth collagen stable isotope values suggests teeth of different ages may serve as ecological chronologies, that could be applied to studies on migration and individual‐level diet variation across diverse time‐scales. Greater understanding of tooth replacement rates, isotopic turnover and associated fractionation of tooth collagen will help refine potential ecological inferences, outlining clear goals for future scientific inquiry.