Comparison of fin and muscle tissues for analysis of signature fatty acids in tropical euryhaline sharks

Assessing the Functional Limitations of Lipids and Fatty Acids for Diet Determination: The Importance of Tissue Type, Quantity, and Quality

“…Recent studies have suggested that differences in FA profiles between muscle and sub-dermal tissue of euryhaline elasmobranches are species-specific (Every et al, 2016). However, when we include the FA profiles of manta ray muscle from Couturier et al (2013) and whale shark sub-dermal tissue, from Rohner et al (2013) in the PCO with our white shark samples, the manta ray and whale shark FA profiles align with the tissuespecific clusters (Figure 1).…”

“…As such, these tissues may therefore present complementary results, reflecting diets incorporated across different time frames (Every et al, 2016). Given the opportunity to collect both tissue types through non-lethal biopsies, further investigations comparing the tissue-specific FA incorporation rates should be undertaken.…”

“…Instead, minimally invasive biopsy techniques are often employed to obtain tissue samples for biochemical studies (e.g., Hooker et al, 2001;Carlisle et al, 2012;Hussey et al, 2012). With the development of specialized biopsy probes (Reeb and Best, 2006;Robbins, 2006;Daly and Smale, 2013), tissue samples can be obtained from free-swimming marine organisms, reducing the stress and detrimental effects of the capture and release process, and enabling the increased use of FA analyses across a number of species, including threatened elasmobranchs Rohner et al, 2013;Every et al, 2016).…”

“…How these tissue-specific physiological and biochemical differences manifest in FA profiles remains poorly studied, with most elasmobranch work to date focused on the FA differences between skeletal muscle and the lipid-rich liver (e.g., Schaufler et al, 2005;Pethybridge et al, 2011;Beckmann et al, 2013), myocardial tissue (Davidson et al, 2011(Davidson et al, , 2014, and blood plasma (Ballantyne et al, 1993;McMeans et al, 2012). However, Every et al (2016) recently showed differences in FA profiles between muscle tissue and fin clips (a mixed-tissue sample, including cartilage, connective tissue, muscle, vascularization and an outer dermal layer with denticles).…”

“…Although small amounts of tissue are sufficient for genetic [1 mg dry weight (DW), Kasajima et al, 2004] and stable isotope analysis (∼10 mg DW, Jaime-Rivera et al, 2013), the minimum amount of muscle or sub-dermal tissue necessary for accurate FA analysis remains relatively unknown. Although Every et al (2016) reported that FA were detectable in fin clips as small as 20 mg and muscle biopsies >10 mg dry weight, minimum sample sizes yielding consistent results were not quantitatively assessed. Such evaluations are vital however, particularly when considering the appropriateness of various biopsy probes, and the applicability of the sampling method across smaller elasmobranch species, from which removing large amounts of tissue is not feasible.…”