Elements and elasmobranchs: hypotheses, assumptions and limitations of elemental analysis

Abstract

Quantifying the elemental composition of elasmobranch calcified cartilage (hard parts) has the potential to answer a range of ecological and biological questions, at both the individual and population level. Few studies, however, have employed elemental analyses of elasmobranch hard parts. This paper provides an overview of the range of applications of elemental analysis in elasmobranchs, discussing the assumptions and potential limitations in cartilaginous fishes. It also reviews the available information on biotic and abiotic factors influencing patterns of elemental incorporation into hard parts of elasmobranchs and provides some comparative elemental assays and mapping in an attempt to fill knowledge gaps. Directions for future experimental research are highlighted to better understand fundamental elemental dynamics in elasmobranch hard parts.

Natural variability and effects of cleaning and storage procedures on vertebral chemistry of the blacktip shark Carcharhinus limbatus

“…The use of bleach to aid in tissue removal is a common practice and the results indicate that brief exposure to bleach did not have a significant effect on vertebral chemistry. This is consistent with the findings of Tillett et al (2011) andMcMillan et al (2017). Because bleach is not commonly used during otolith processing, there is little need to test for potential affects.…”

“…() and McMillan et al . (). Because bleach is not commonly used during otolith processing, there is little need to test for potential affects.…”

“…Elasmobranch researchers typically rely on diluted bleach to aid in tissue removal before storing vertebrae in isopropanol or ethanol prior to sectioning for age and growth analysis (Hale & Baremore, 2013). Although the use of bleach does not appear to affect vertebral chemistry significantly (Tillett et al, 2011;McMillan et al, 2017), the effects of a liquid preservative on vertebral chemistry is unknown but of concern given liquid preservatives can alter otolith chemistry (Milton & Chenery, 1998;Hedges et al, 2004). For example, Milton & Chenery (1998) and Hedges et al (2004) noted that preservation of otoliths or whole fish in ethanol did not significantly alter chemical constituents that are likely to substitute for calcium in the carbonate matrix (e.g.…”

Effects of sample cleaning and storage on the elemental composition of shark vertebrae

“…The analytical sampling period of 0.2842 s, equivalent to a reading every 2.842 μm, corresponded to 90% measurement time. The time‐resolved intensities were converted into concentration (ppm) equivalents using Iolite software (University of Melbourne, Hellstrom et al) with 43 Ca as the internal standard and a Ca index value of 35 weight % . The concentrations were expressed in ppm and as molar ratios to calcium, except for 43 Ca, which was expressed as raw counts per second (CPS).…”

“…Previous research has focused on calcified structures in teleost fish (i.e. otoliths, scales, spines), but recent work has expanded to calcified structures in elasmobranchs including vertebrae, jaws and teeth . Shark vertebrae centra are widely used for determining age due to concentric growth, non‐resorption of accreted material and seasonally influenced rates of mineralization .…”