Estimating stable isotope turnover rates of epidermal mucus and dorsal muscle for an omnivorous fish using a diet-switch experiment

© 2018, The Author(s). Stable isotope (SI) analysis studies rely on knowledge of isotopic turnover rates and trophic-step discrimination factors. Epidermal mucus (‘mucus’) potentially provides an alternative SI ‘tissue’ to dorsal muscle that can be collected non-invasively and non-destructively. Here, a diet-switch experiment using the omnivorous fish Cyprinus carpio and plant- and fish-based formulated feeds compared SI data between mucus and muscle, including their isotopic discrimination factors and turnover rates (as functions of time T and mass G, at isotopic half-life (50) and equilibrium (95)). Mucus isotope data differed significantly and predictively from muscle data. The fastest δ13C turnover rate was for mucus in fish on the plant-based diet (T50: 17 days, T95: 74 days; G50: 1.08(BM), G95: 1.40(BM)). Muscle turnover rates were longer for the same fish (T50: 44 days, T95: 190 days; G50: 1.13(BM), G95: 1.68(BM)). Longer half-lives resulted in both tissues from the fish-based diet. δ13C discrimination factors varied by diet and tissue (plant-based: 3.11–3.28‰; fishmeal: 1.28–2.13‰). Mucus SI data did not differ between live and frozen fish. These results suggest that mucus SI half-lives provide comparable data to muscle, and can be used as a non-destructive alternative tissue in fish-based SI studies

Multiple Testprozeduren zur Identifikation sinnvoller Dosiskombinationen in bifaktoriellen Plänen

Hung, Chi, and Lipicky proposed the AVE and MAX tests to analyse in a bifactorial design whether combinations of two drugs at several doses fulfil the desirable property of superiority to both their single drug components. These are global tests and do not identify the special combinations which are more effective than their respective single components. Here multiple testing procedures based on linear contrast tests and on the closed testing principle will be presented. They will be compared with simultaneous Min tests of Laska and Meisner. The performance of these approaches is investigated by simulation studies.Die von Hung, Chi und Lipicky vorgeschlagenen AVE- und MAX-Tests ermöglichen die Analyse in einem bifaktoriellen Plan, ob Kombinationen von zwei Medikamenten mit verschiedenen Dosen existieren, die die wünschenswerte Eigenschaft der Überlegenheit zu beiden Einzelkomponenten besitzen. Die Tests sind jedoch globale Tests und können keine speziellen Dosis-Kombinationen identifizieren, die effektiver sind als ihre beiden Einzelkomponenten. In dieser Arbeit werden multiple Testprozeduren vorgeschlagen, die auf linearen Kontrast-Tests und dem Abschlusstest-Prinzip beruhen. Ein Vergleich mit simultanen Min-Tests nach Laska und Meisner wird angestellt sowie das Verhalten dieser Ansätze anhand von Simulationsstudien untersucht