DOI: 10.5061/dryad.hqbzkh1g5
title: Data from: Metabolic proxy for cephalopods: Stable carbon isotope values recorded in different biogenic carbonates

description: 1. Measuring the metabolic rate of marine animals in their natural
 environment is challenging, impeding our understanding of their
 physiological ecology. Recently, a novel metabolic proxy, namely the δ13C
 values of biogenic carbonates (otoliths), was experimentally validated in
 teleost fishes. Cephalopods possess several types of biogenic carbonates,
 such as statolith, cuttlebone, and other internal and external shells,
 which are all potential metabolic recorders, but few have been evaluated.
 2. To test the feasibility of the δ13C metabolic proxy in cephalopods, we
 conducted a temperature-controlled experiment with the pharaoh cuttlefish
 Sepia pharaonis to assess whether the proportion of metabolically derived
 carbon (Cresp) incorporated into statoliths and cuttlebones increases with
 metabolism in a warm environment. Moreover, we conducted multiple-species
 analysis by using the published δ13C values of various biogenic carbonates
 to evaluate the consistency of the proxy among cephalopod species and
 between cephalopods and teleost fishes. 3. In the temperature-controlled
 laboratory experiment, Cresp values calculated from statoliths and
 cuttlebones increased with an increase of environmental temperature. Cresp
 values did not differ between statoliths and cuttlebones. Moreover, the
 Cresp values of cephalopod biogenic carbonates had a similar range to
 those of fish otoliths and were correlated with metabolism-related
 factors, such as ambient temperature, body mass, ontogeny, and functional
 behaviours, strengthening the feasibility of their use. 4. The δ13C
 metabolic proxy reflects the total energy used in the natural environment,
 and it can be transformed into the oxygen consumption rate for a broader
 comparison with other species and for further evaluation with current
 theories related to metabolic ecology. However, experimental validation is
 highly recommended because the relationship between the oxygen consumption
 rate and Cresp values derived from biogenic carbonates of cephalopods
 might be structure- and species-specific. Our study revealed that the
 newly developed metabolic proxy provides a valuable alternative approach
 to studying ecophysiology in cephalopods, and further development might
 broaden its applicability. --
description: Ten cephalopod
 species with δ<sup>13</sup>C and δ<sup>18</sup>O
 values from the literature were used in analyses of this study.
 δ<sup>13</sup>C and δ<sup>18</sup>O values were
 derived from external (<i>Nautilus </i>and
 <i>Argonauta</i>) and internal shells (ram’s horn squids and
 cuttlefishes) as well as statoliths (squids). The experienced temperature
 was extracted from the same study. If recorded temperatures were absent in
 previous studies, we estimated temperatures from the reported
 δ<sup>18</sup>O values by using the temperature-dependant
 equations. The
 C<sub>resp</sub> value was estimated based on the
 δ<sup>13</sup>C values of biogenic carbonates by using the
 two-component mixing model. In the model, the
 δ<sup>13</sup>C<sub>DIC</sub> values were based on
 published data in the same sampling area. The
 δ<sup>13</sup>C<sub>diet</sub> values were derived
 from the δ<sup>13</sup>C values in other tissues/structures
 (muscle, beaks, or organic matter in biogenic carbonate) minus assumed
 trophic enrichment factor 1, but for planktivores, the
 δ<sup>13</sup>C<sub>diet</sub> values were
 obtained from the δ<sup>13</sup>C values of zooplankton in the
 sample areas according to published spatial ocean
 modelling.
description: The parameters in the dataset are described in the README file
 and the source of isotope values is shown in the dataset.