Different techniques have been used to estimate assimilation in aquatic organisms. Indirect methods may use indigestible markers such as ash or chromic oxide measured in food and faeces to determine apparent assimilation efficiency (Conover, 1966; Bordner et al., 1983; Goodman-Lowe et al., 1999), assessment of energy loss as excretory products (Drazen et al., 2007) or determining the elemental composition of ingested food sampled from different segments of the digestive tract (Quinn, 1986). The availability of purified radio-isotopes allows tracing of isotope-labelled nutrients within organisms, enabling estimation of ingestion, assimilation and respiration rates by direct rather than indirect methods (e.g. Britz, et al., 1997; Lu et al., 2006). However, the use of radioactive isotopes is subject to a number of safety regulations (Schlechtriem et al., 2004) and the dilution factor is relatively fast, so their use is generally limited to short-term tracing of dietary components. In contrast, stableisotopes are non-hazardous, non-invasive and the changing ratio of stableisotopes in tissues can be used to determine the contribution of dietary sources to growth over longer periods in individuals or at the population level. Different food items have different isotopic signatures and different isotopes of the same element are incorporated in tissues at different rates, therefore in ecological studies they can be used to infer trophic linkages (Van der Zanden et al., 1998), providing an integration of feeding over time (Peterson and Fry, 1987) and also allowing the use of mixing and mass balance models to estimate the relative contribution of different food sources (Burford et al., 2004). The application of these techniques and models has also supported experimental investigation of nutrition in crustaceans, in studies using either naturally-occurring or artificially-enriched stableisotopes in compound diets (Parker et al., 1989; D’Avanzo et al., 1991; Preston et al., 1996). In an extension of ecological food web studies, naturally-occurring stableisotopes in live plankton have been used to investigate the fate of nutrients in hatchery systems where several food sources are present (Schlechtriem et al., 2004; Jomori et al., 2005; Results from Chapter 3) and to assess carbon and nitrogen turnover rates (Fry and Arnold, 1982; Hesslein et al., 1993; MacAvoy et al., 2005).
13 (Carter et al., 1994, 1998; Beltran et al., 2008) and the rate of protein turnover has been determined in several fish and crustaceans species (see reviews by Houlihan et al., 1995a; Waterlow, 2006; Fraser and Rogers, 2007). Protein turnover rates have been frequently estimated by the flooding dose method (Garlick et al., 1980; Houlihan et al., 1988) using radioactive isotopes ( 14 C-labelled lysine or 3 H-labelled phenylalanine) that are incorporated through injection or constant infusion as metabolic tracers into the free amino-acid pool (Waterlow, 2006). The metabolism of proteins has also been evaluated using stable isotope tracers as an alternative to radioactive isotopes. Protein synthesis studies in trout (Oncorhynchus mykiss) have shown that results obtained using enriched stableisotopes are similar to those obtained using radio-labelled amino-acids (Houlihan et al., 1995a). Carter et al. (1994, 1998) used stableisotopes in trout (O. mykiss) and flounder (Pleuronectes flesus) in order to assess protein synthesis, protein turnover rates and to construct nitrogen budgets. Conceição et al. (2001) extended this approach to larval turbot (Psetta maxima) using 15 N- labelled rotifers to demonstrate that exposure to an immunostimulant increased the fractional rates of protein synthesis.
contribution in crustacean larvae using stableisotopes is difficult due to rapid ontogeny through larval stages and trophic levels, which frequently prevent the organisms form reaching isotopic equilibrium. However, as observed in the present study, the very fast growth of penaeid larvae and PL (fed on 100, 75 and 50% of Artemia nauplii) achieved isotopic equilibrium with the diets in as little as 5 d. The use of isotopic mixing models is limited when the dietary sources have overlapping isotopic profiles. Evaluation of nutrient incorporation thus requires previous knowledge (or estimation) of the diet isotopic values in order to ensure enough resolution on the isotopic changes occurring in tissue over time as a result of dietary intake. Although the use of live feeds represents clear advantages in the culture of marine larvae such as high digestibility, availability in the water column and suitability for nutritional enrichment, they are expensive to culture and provide a vector for the introduction of pathogenic micro-organisms into larval culture tanks (Southgate and Partridge, 1998), therefore, there are continuous efforts in developing and improving inert diets that can be used at higher replacement levels. In this regard, the use of stableisotopes provides an additional useful tool in assessing nutrient incorporation from
and fish meal (FM) were used to estimate the relative contribution of dietary nitrogen supplied by both ingredients to the somatic growth of juvenile channel catfish Ictalurus punctatus. Six isonitrogenous and isoenergetic experimental diets were formulated using FM and PBM. Two of these diets consisted of isotopic controls having only one ingredient supplying dietary nitrogen, either FM or PBM. Four combined diets were formulated with varying proportions of these ingredients in order to supply high proportions of PBM (FM:PBM, 50:50, 35:65 20:80 and 5:95) on a nitrogen basis. There were significant differences in mean final weight of fish at the end of the trial. Lower growth was observed as the dietary level of PBM increased. In order to determine the relative contributions of the dietary nitrogen supplied by FM and PBM to catfish growth, an isotopic mixing model was applied. Results indicated that the incorporation of dietary nitrogen supplied by PBM was equivalent to the die tary proportions. The dietary nitrogen available in combined diets containing 50, 65 and 80% of PBM was incorporated in fish bodies as 50, 62 and 81%, respectively. However, high incorporation of dietary nitrogen from PBM was not always reflected in higher growth rates. Results demonstrate the viable use of stableisotopes to determine the allocation of dietary nitrogen and indicate that practical diets for catfish can be formulated with levels of PBM as high as 65% without affecting growth and survival.
commercial availability of these analytical techniques, together with laboratory instrumentation having increasing accuracy levels, has allowed tracing nutrients in different organisms and ecosystems. The sampling techniques for a representative nutritional study using stableisotopes should consider all the possible sources of nutrients for the target organism. Considerations on analyzing whole animal carcass or specific tissues of the consuming organism are defined according to the aim of the study (e.g. muscle tissue to trace dietary nitrogen, whole bodies to trace dietary carbon). Sample pretreatment of solid samples includes drying, grinding and lipid extraction (for samples containing high lipid levels, as lipids are isotopically depleted in 13 C) and/or acidification to remove inorganic carbon. The isotopes are thus an integral part of the organic tissues but compounds having heavy isotopes can also be added to a specific substrate in order to label it or enrich (“spike”) it. In contrast to the radio-isotopes, the stableisotopes can be measured at natural abundance levels and are not dangerous, they are not invasive and several estimations can be done on a population, individual or specific tissue. Additional applications of the isotopic techniques include their use as pollution biomarkers (e.g. aquaculture waste tracing, Felsing et al. 2006) and their application in estimating metabolic turnover rates (MacAvoy et al. 2006), authenticating production methods (e.g. wild vs. farmed fish, Serrano et al. 2007), tracing animal migrations (Fry et al. 2003) and reconstructing palaeodiets (Richards et al. 2006).
The cave bear presents a specific tooth morphology with wide grinding surfaces, and muscle insertions in the skull and the jaw which show a great biting power, which is the reason why it is thought to follow a basically herbivorous diet (KURTÉN, 1976). In recent years, diffe- rent approaches have been followed as to the reconstruction of this species´ diet through the analysis of stableisotopes, usually 13 C and 15 N, preferably in bone
5 (Phillips, 2012). In aquaculture nutrition, the isotopic values of carbon and nitrogen have been used as natural biomarkers to estimate dietary contributions in organisms fed on experimental dietary formulations having ingredients with contrasting isotopic signatures (Martínez-Rocha et al., 2013; Gamboa-Delgado et al., 2013, 2014). The different dietary resources found in aquatic and terrestrial ecosystems frequently show distinct δ 15 N values due to the effect of characteristic nutrient flows and metabolic pathways. However, this natural flow of nutrients (and isotopes) is altered under the controlled, artificial systems promoting the growth of commercial valuable microorganisms from specific substrates. The present study employed the isotopic differences found in torula yeast and fish meal to assess the relative incorporation of dietary nitrogen and total dry matter supplied by these sources to the growth of Pacific white shrimp by means of an isotope mixing model.
ical evidence to propose an explanation of how T. landbeckii dunes form. Contrary to wind‐blown dunes, the systems studied here actually grow against the main wind direction, which would explain their unusual layered stratigraphy. We also examined a number of parameters preserved in the buried T. landbeckii layers, including stable carbon and nitrogen isotopes. Stratigraphic and stable carbon isotope evidence clearly points to a link between T. landbeckii leaf burial and the generation of distinct “cap” carbonates. This process occurs in a similar fashion to the development of soil carbonate but instead of precipitation of biologi- cally respired CO 2 , we suspect that oxidation of calcium
A. caballeroi depicts a large head, upwardly facing mouth position, fusiform body, and conical teeth, consistent with the capture of elusive preys and access to floating terrestrial insects (e.g., hy- menopterans or coleopterans) (Bonato et al., 2017). In contrast, A. aeneus had a relatively deeper body and shorter snout, which is associated with the ability to move upward and downward in the water column, from the bottom to the surface, as befits an om- nivorous species (Gatz, 1979; Mise et al., 2013; Winemiller, 1991). In conclusion, the Astyanax aeneus and A. caballeroi model sys- tem showed a significant correlation between ecomorphological traits and trophic habits (i.e., stableisotopes values), supporting the hypothesis that morphological divergence in trophic- related traits is associated with niche partitioning. This study also provides addi- tional evidence that trophic partitioning could trigger morphological changes and ultimately promote speciation, as seen in other groups of fishes.
Incentives: Centralized matching algorithms like the one proposed in this paper are often used in economic settings where agents are self-interested and might alter their submitted preference list in order to improve their match. It is known that no stable mechanism can be incentive-compatible for both jobs and ma- chines. In a job-optimal mechanism, for example, machines have an incentive to lie. However, Immorlica and Mahdian  showed that, in a one-to-many match- ing, if preference lists of jobs are short and preferences are drawn randomly according to a particular class of distributions, then each agent has a unique stable partner with high probability, and thus has no incentive to lie. It would be interesting to prove a similar statement in the many-to-many setting studied here.
The expression i)-iii) in the example tells us that under those conditions on c andδ the complete, empty and the star network belong to set of stable network. The main and subtle difference between this treatment of networks and the usual one is just conceptual because we are introducing the concept of coalition, preferences and consistent set. We are given a tool that allows players to behave in a farsighted way. Farsightedness behavior allows the coalition to consider the possibility that once it acts, another coalition might react and, a third coalition might in turn react, and so on, virtually, without limit. It is clear that the notion of SIP plays an important roll in the change of the network. This change has to be carried out through a SIP. In other words, we mean that if we allow players to look arbitrarily far ahead they will only follow an improved path. Since players receive their payoffs only when the process is over the concept of SIP will not be myopic. See Watts (2001) and Jackson and Watts (2001) for a wide discussion about myopic players.
Evolutionary dynamics is defined considering an imitative revision protocol, in particular, pairwise imitation. The imitative dynamics admits a unique asymptoti- cally stable equilibrium. The nature of this stable equilibrium depends on the char- acteristics which describe the populations of Sanchos and Quixotes, as well as on the size of these populations. If the warm-glow that Quixotes attach to compliance is not too large, or equivalently if the ratio of Sanchos in the global population is low, then this equilibrium is characterized by zero compliance among Sanchos and a positive compliance rate (but not complete compliance) for Quixotes. Alternatively, if the warm-glow for Quixotes is high, then all Quixotes comply together with some Sanchos. What determines this latter equilibrium is a high degree of dissimilarity between Sanchos and Quixotes and particularly, a strong warm-glow from com- pliance rather than a strong cold-prickle from defection. Moreover, the size o the population of Sanchos also increases the likelihood that some Sanchos imitate the compliant behavior of Quixotes.