Isotopic incorporation rates for shark tissues from a long-term captive feeding study

Abstract

SUMMARYStable isotope analysis has provided insight into the dietary and habitat patterns of many birds, mammals and teleost fish. A crucial biological parameter to interpret field stable isotope data is tissue incorporation rate, which has not been well studied in large ectotherms. We report the incorporation of carbon and nitrogen into the tissues of leopard sharks (Triakis semifasciata). Because sharks have relatively slow metabolic rates and are difficult to maintain in captivity, no long-term feeding study has been conducted until the point of isotopic steady state with a diet. We kept six leopard sharks in captivity for 1250days, measured their growth, and serially sampled plasma, red blood cells and muscle for stable carbon and nitrogen isotope analysis. A singlecompartment model with first-order kinetics adequately described the incorporation patterns of carbon and nitrogen isotopes for these three tissues. Both carbon and nitrogen were incorporated faster in plasma than in muscle and red blood cells. The rate of incorporation of carbon into muscle was similar to that predicted by an allometric equation relating isotopic incorporation rate to body mass that was developed previously for teleosts. In spite of their large size and unusual physiology, the rates of isotopic incorporation in sharks seem to follow the same patterns found in other aquatic ectotherms.

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

“…The underlying physiological differences between the two tissue types (muscle, a metabolically active and protein-rich tissue vs. sub-dermal tissue, a less bioactive and largely structural tissue composed of elastin and collagen) results in distinct biochemical properties, with the potential to yield different ecological data. This is evidenced by recent isotopic studies on white sharks, Carcharodon carcharias, whereby muscle and subdermal tissue had the same 15 N isotopic signatures, but divergent 13 C signatures, which was attributed to differing tissue-specific incorporation rates (Carlisle et al, 2012;Kim et al, 2012;JaimeRivera et al, 2013). 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).…”

Diet shift and site-fidelity of oceanic whitetip sharks Carcharhinus longimanus along the Great Bahama Bank

“…Muscle tissue samples were thawed and thoroughly rinsed in DI water (3× sonication) to extract urea (e.g. Kim et al 2012b). Samples were then frozen at −80°C for 24 h, lyophilized for 72 h, and homogenized using a Wig-LBug (Sigma Aldrich).…”

“…SIA uses the ratio of heavy to light isotopes in an organism to represent long-term integration of diet into various tissues (Fry 2006). In elasmobranchs, blood plasma has been shown to represent relatively short (70 to 200 d) periods of time (Matich et al 2011, Kim et al 2012b, while muscle tissue represents diet over longer (400 to 600 d) timeframes (MacNeil et al 2006, Matich et al 2011, Kim et al 2012b. Oceanic whitetips return to The Bahamas in October to November, and sharks were sampled at CI in early May (Howey-Jordan et al 2013); thus, sharks had likely been at CI for several months (i.e.…”

Environmental and Individual Factors Shaping the Habitat Use and Trophic Interactions of Juvenile Bull Sharks (Carcharhinus leucas) in a Subtropical Estuary

“…The remaining 1 mL of blood was retained in its original composition (whole blood, "blood" hereafter). Based on several lab studies, plasma has an isotopic half-life of ~32 days in elasmobranchs (Kim et al 2012), and likely serves as a short-term diet indicator for juvenile bull sharks, while blood has an isotopic half-life of ~61 days , and likely serves as a longer-term diet indicator for juvenile bull sharks. As such, when more dynamic plasma δ 13 C values are compared to more stable blood δ 13 C values they can be used to study short-term changes in the diets of sharks, and provide diet information over the time-frame juvenile bull sharks may respond to the pulse of marsh prey into the Shark River Estuary.…”

“…Both Kim et al (2012) and Malpica-Cruz et al (2012) investigated isotopic discrimination in captive leopard sharks (Triakis semifasciata; n = 6, n = 16, respectively). Kim et al (2012) ).…”