RESUMO
Nitrogen stable isotopes ratios (δ15 N) were determined for selected tissues (muscle, liver, blood and yolk) of pregnant females and their embryos of a placental viviparous species, the Pacific sharpnose shark (Rhizoprionodon longurio), and a yolk-sac viviparous species, the speckled guitarfish (Pseudobatos glaucostigmus). The R. longurio embryo tissues were 15 N enriched compared to the same tissues in the pregnant female, using the difference in δ15 N (Δδ15 N) between embryo and adult. Mean Δδ15 N was 2.17 in muscle, 4.39 in liver and 0.80 in blood. For P. glaucostigmus, embryo liver tissue was significantly 15 N enriched in comparison with liver of the pregnant female (Δδ15 N mean = 1.22), whereas embryo muscle was 15 N depleted relative to the muscle of the pregnant female (Δδ15 N mean = -1.22). Both species presented a significant positive linear relationship between Δδ15 N and embryo total length (LT ). The results indicated that embryos have different Δδ15 N depending on their reproductive strategy, tissue type analysed and embryo LT .
Assuntos
Isótopos de Nitrogênio/metabolismo , Reprodução/fisiologia , Tubarões/fisiologia , Viviparidade não Mamífera/fisiologia , Animais , Feminino , Músculos/metabolismo , Isótopos de Nitrogênio/análise , Tubarões/classificaçãoRESUMO
This study investigated the dose-dependent response in lamb meat of stable nitrogen isotope ratio to the dietary proportion of legumes, and the ability of the nitrogen isotope signature of the meat to authenticate meat produced from legume-rich diets. Four groups of nine male Romane lambs grazing a cocksfoot pasture were supplemented with different levels of fresh alfalfa forage to obtain four dietary proportions of alfalfa (0%, 25%, 50% and 75%) for 98 days on average before slaughter (groups L0, L25, L50 and L75). We measured the stable nitrogen isotope ratio in the forages and in the longissimus thoracis muscle. The δ(15)N value of the meat decreased linearly with the dietary proportion of alfalfa. The distribution of the δ(15)N values of the meat discriminated all the L0 lambs from the L75 lambs, and gave a correct classification score of 85.3% comparing lambs that ate alfalfa with those that did not.
Assuntos
Ração Animal/análise , Fabaceae/química , Carne/análise , Isótopos de Nitrogênio/análise , Ovinos/metabolismo , Fenômenos Fisiológicos da Nutrição Animal , Animais , Análise Discriminante , Fabaceae/metabolismo , Controle de QualidadeRESUMO
The δ15N composition of bottom-feeding fish (iliophagous = Apareiodon affinis, Cyphocharax nagelii, Prochilodus lineatus, Steindachnerina brevipinna and S. insculpta; detritivorous = Loricariichthys platymetopon and Liposarcus anisitsi; benthophagous = Satanoperca pappaterra and Hoplosternum littorale) and their primary food sources were investigated in the upper Paraná River floodplain during rainy seasons in different environments (lotic and lentic). Two hypotheses were tested: i) that the trophic position and isotopic values of the investigated organisms (fish and food resources) vary spatially; and ii) that trophic position and isotopic compositions differ among iliophagous, detritivorous and benthophagous fish. C4 macrophytes, periphyton and phytoplankton were isotopically different in sites analyzed. Significant isotopic differences occurred in the species of each trophic category. Spatial differences were observed in the isotopic composition of P. lineatus and L. platymetopon, whose values were more enriched in the Paraná River and Pau Véio Lake. Significant spatial differences in trophic position were observed for L. platymetopon and H. littorale, which presented the highest values in the Paraná and Baía rivers, respectively. Trophic positions were significantly different among the species that composed each trophic category. These findings demonstrate that in energy-flow studies in detrital food chains generalizations concerning the grouping of fish into trophic categories and/or habitats should only be carried out after careful investigations of the local/specific trophic dynamics of the organisms.
A composição de δ15N de peixes exploradores de fundo (iliófagos = Apareiodon affinis, Cyphocharax nagelii, Prochilodus lineatus, Steindachnerina brevipinna e S. insculpta; detritívoros = Loricariichthys platymetopon e Liposarcus anisitsi; e bentófagos = Satanoperca pappaterra e Hoplosternum littorale) e suas fontes alimentares foram investigadas na planície de inundação do alto rio Paraná durante a estação de chuvas em ambientes lóticos e lênticos. Duas hipóteses foram testadas: i) que a posição trófica e os valores isotópicos dos organismos investigados (peixes e fontes alimentares) variam espacialmente; e ii) que a posição trófica e a composição isotópica diferem entre os peixes iliófagos, detritívoros e bentófagos. Macrofitas C4, perifíton e fitoplâncton foram isotopicamente diferentes entre os locais analisados. Diferenças isotópicas ocorreram entre as espécies de cada categoria trófica. Diferenças espaciais foram observadas na composição isotópica de P. lineatus e L. platymetopon, as quais tiveram valores mais enriquecidos no rio Paraná e ressaco do Pau Véio. Diferenças espaciais significativas nas posições tróficas foram verificadas para L. platymetopon e H. littorale, as quais apresentaram os maiores valores nos rios Paraná e Baía, respectivamente. As posições tróficas foram significativamente diferentes entre as espécies que compuseram cada categoria trófica. Estes resultados demonstram que em estudos de fluxo de energia em cadeias alimentares detritais generalizações a respeito do agrupamento de peixes em categorias tróficas e/ ou habitats devem ser conduzidos somente após investigações criteriosas da dinâmica trófica local/ específica dos organismos.