Natural carbon stable isotope ratios as indicators of the relative contribution of live and inert diets to growth in larval Senegalese sole (Solea senegalensis)

Abstract

The relative contributions of live Artemia metanauplii and an inert diet for growth of Senegalese sole larvae and postlarvae were assessed through the analysis of carbon stable isotopes ratios (δ 13 C) in both diets and whole larval tissue. Larvae were reared on four dietary regimes: 100% live prey (rotifers and Artemia), 100% inert formulated diet and two co-feeding regimes of 70:30 and 30:70 ratios of Artemia and inert diet, respectively. Larvae from the live food regime and both co-feeding regimes showed a steep increase in δ 13C from 10 days after hatching (DAH) as a result of the onset and continuation of Artemia consumption. From 12 DAH fish larvae from all the regimes showed significant isotopic differences as their δ senegalensis larvae may be adjusted to meet ontogenetic changes in the capacity for larvae to utilise inert diets. The contrasting levels of carbon isotope discrimination between diet and tissue in larvae reared on either 100% live feed or 100% inert diet 3 indicate relatively poor utilization of nutrients from the inert diet. The use of isotopic discrimination factors as potential indicators of the digestive physiological performance of a consuming organism in regards to its diet is discussed.

Artemia replacement in co-feeding regimes for mysis and postlarval stages of Litopenaeus vannamei: Nutritional contribution of inert diets to tissue growth as indicated by natural carbon stable isotopes

“…Carbon contents in Artemia nauplii and inert diets were similar; therefore, no corrections were applied to estimate carbon contributions from the two sources (Fry, 2006;Gamboa-Delgado et al, 2008). Results from the isotope mixing model indicate that observed carbon contributions from Artemia nauplii were significantly higher (P<0.001) than expected contributions indicated by the carbon proportions established in the three co-feeding regimes (Tables 1 and 4), while nutritional contributions from the inert diet were lower than expected.…”

“…Pre-analysis sample preparation and analytical methods for determination of carbon and nitrogen contents, carbon isotopic ratios (δ 13 C) and procedures to estimate proportional nutrient contribution from inert diets and Artemia using a two-source, one-isotope mixing model (Phillips and Gregg, 2001) are described in Gamboa-Delgado et al (2008). Carbon isotope discrimination factors (∆ 13 C) were estimated as the difference between δ 13 C mean values of shrimps and the δ 13 C of their respective diets after reaching isotopic equilibrium.…”

“…However, the use of radioactive isotopes is limited to shortperiod studies and since radio-labels can be hazardous, they are subject to many regulations and restrictions; as a consequence, their use has been largely replaced by stable isotope tracers in studies of human and animal metabolism over the past 30 years (Schlechtriem et al, 2004;Conceição at al., 2007). The use of stable isotopes is a safe and useful technique that has been applied to determine nutrient incorporation from different dietary items in aquatic larval organisms (Schlechtriem et al, 2004;Jomori et al, 2008;Gamboa-Delgado et al, 2008). Estimation of nutrient retention in crustacean larvae is difficult due to their small size and the rapid and complex larval development, which increases the challenge in accurately assessing incorporation of nutrients into larval tissue.…”

Stable carbon and nitrogen incorporation in blood and fin tissue of the catfish Pterygoplichthys disjunctivus (Siluriformes, Loricariidae)

“…Most studies of isotopic incorporation in fishes have been performed with juvenile animals that grow a) Pterygoplichthys disjunctivus Table 3) were used to analyze the isotopic signatures of the animals in plot b. CBOM=coarse benthic organic matter at a rapid pace (Hesslein et al 1993;Suzuki et al 2005;Trueman et al 2005;Vollaire et al 2007;Zuanon et al 2007;Gamboa-Delgado et al 2008). Thus, in these studies, rates of isotopic incorporation were similar to growth rate and, therefore, mostly reflective of new tissue accretion.…”

Naturally-occurring stable isotopes as direct measures of larval feeding efficiency, nutrient incorporation and turnover

“…In contrast, studies that take advantage of the natural isotopic composition of dietary components may be designed to investigate integrated measures of ingestion, assimilation and growth over longer time periods under normal feeding and environmental conditions. To date, relatively few studies have adopted this approach, which is particularly useful in determining the sources and fate of nutrients (Schlechtriem et al, 2004;Jomori et al, 2005;Gamboa-Delgado et al, 2008) and in assessing tissue carbon and nitrogen turnover rates (Hesslein et al, 1993;Herzka et al, 2001;Gamboa-Delgado et al, 2008;Gamboa-Delgado and Le Vay, 2009b). Unlike the very high levels of heavy isotopes present in enriched feeds, natural abundance of carbon and nitrogen isotopes is very strongly biased toward the lighter 12 C and 14 N isotopes, and the differences in isotopic signature between dietary components is small.…”