Dataset Information

Teleost and elasmobranch eye lenses as a target for life-history stable isotope analyses.

ABSTRACT: Incrementally grown, metabolically inert tissues such as fish otoliths provide biochemical records that can used to infer behavior and physiology throughout the lifetime of the individual. Organic tissues are particularly useful as the stable isotope composition of the organic component can provide information about diet, trophic level and location. Unfortunately, inert, incrementally grown organic tissues are relatively uncommon. The vertebrate eye lens, however, is formed via sequential deposition of protein-filled fiber cells, which are subsequently metabolically inert. Lenses therefore have the potential to serve as biochemical data recorders capturing life-long variations in dietary and spatial ecology. Here we review the state of knowledge regarding the structure and formation of fish eye lenses in the context of using lens tissue for retrospective isotopic analysis. We discuss the relationship between eye lens diameter and body size, describe the successful recovery of expected isotopic gradients throughout ontogeny and between species, and quantify the isotopic offset between lens protein and white muscle tissue. We show that fish eye lens protein is an attractive host for recovery of stable isotope life histories, particularly for juvenile life stages, and especially in elasmobranchs lacking otoliths, but interpretation of lens-based records is complicated by species-specific uncertainties associated with lens growth rates.

SUBMITTER: Quaeck-Davies K

PROVIDER: S-EPMC5991300 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Teleost and elasmobranch eye lenses as a target for life-history stable isotope analyses.

Quaeck-Davies Katie K Bendall Victoria A VA MacKenzie Kirsteen M KM Hetherington Stuart S Newton Jason J Trueman Clive N CN

PeerJ 20180604

Incrementally grown, metabolically inert tissues such as fish otoliths provide biochemical records that can used to infer behavior and physiology throughout the lifetime of the individual. Organic tissues are particularly useful as the stable isotope composition of the organic component can provide information about diet, trophic level and location. Unfortunately, inert, incrementally grown organic tissues are relatively uncommon. The vertebrate eye lens, however, is formed via sequential deposi ...[more]

PMID: 29888128

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Project description:Consumption of frog legs is increasing worldwide, with potentially dramatic effects for ecosystems. More and more functioning frog farms are reported to exist. However, due to the lack of reliable methods to distinguish farmed from wild-caught individuals, the origin of frogs in the international trade is often uncertain. Here, we present a new methodological approach to this problem. We investigated the isotopic composition of legally traded frog legs from suppliers in Vietnam and Indonesia. Muscle and bone tissue samples were examined for δ15N, δ13C, and δ18O stable isotope compositions, to elucidate the conditions under which the frogs grew up. We used DNA barcoding (16S rRNA) to verify species identities. We identified three traded species (Hoplobatrachus rugulosus, Fejervarya cancrivora and Limnonectes macrodon); species identities were partly deviating from package labeling. Isotopic values of δ15N and δ18O showed significant differences between species and country of origin. Based on low δ15N composition and generally little variation in stable isotope values, our results imply that frogs from Vietnam were indeed farmed. In contrast, the frogs from the Indonesian supplier likely grew up under natural conditions, indicated by higher δ15N values and stronger variability in the stable isotope composition. Our results indicate that stable isotope analyses seem to be a useful tool to distinguish between naturally growing and intensively farmed frogs. We believe that this method can be used to improve the control in the international trade of frog legs, as well as for other biological products, thus supporting farming activities and decreasing pressure on wild populations. However, we examined different species from different countries and had no access to samples of individuals with confirmed origin and living conditions. Therefore, we suggest improving this method further with individuals of known origin and history, preferably including samples of the respective nutritive bases.

Project description:IntroductionHydroponic vegetable cultivation is characterized by high intensity and frequent nitrogen fertilizer application, which is related to greenhouse gas emissions, especially in the form of nitrous oxide (N2O). So far, there is little knowledge about the sources of N2O emissions from hydroponic systems, with the few studies indicating that denitrification could play a major role.MethodsHere, we use evidence from an experiment with tomato plants (Solanum lycopersicum) grown in a hydroponic greenhouse setup to further shed light into the process of N2O production based on the N2O isotopocule method and the 15N tracing approach. Gas samples from the headspace of rock wool substrate were collected prior to and after 15N labeling at two occasions using the closed chamber method and analyzed by gas chromatography and stable isotope ratio mass spectrometry.ResultsThe isotopocule analyses revealed that either heterotrophic bacterial denitrification (bD) or nitrifier denitrification (nD) was the major source of N2O emissions, when a typical nutrient solution with a low ammonium concentration (1-6 mg L-1) was applied. Furthermore, the isotopic shift in 15N site preference and in δ18O values indicated that approximately 80-90% of the N2O produced were already reduced to N2 by denitrifiers inside the rock wool substrate. Despite higher concentrations of ammonium present during the 15N labeling (30-60 mg L-1), results from the 15N tracing approach showed that N2O mainly originated from bD. Both, 15N label supplied in the form of ammonium and 15N label supplied in the form of nitrate, increased the 15N enrichment of N2O. This pointed to the contribution of other processes than bD. Nitrification activity was indicated by the conversion of small amounts of 15N-labeled ammonium into nitrate.Discussion/conclusionComparing the results from N2O isotopocule analyses and the 15N tracing approach, likely a combination of bD, nD, and coupled nitrification and denitrification (cND) was responsible for the vast part of N2O emissions observed in this study. Overall, our findings help to better understand the processes underlying N2O and N2 emissions from hydroponic tomato cultivation, and thereby facilitate the development of targeted N2O mitigation measures.

Dataset Information

Teleost and elasmobranch eye lenses as a target for life-history stable isotope analyses.

Publications

Teleost and elasmobranch eye lenses as a target for life-history stable isotope analyses.

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