Fluorescence anisotropy of branched molecules containing 1-aminopyrene chromophores.

Fluorescence anisotropy measurements were performed on a set of multichromophoric compounds, which contain a different number of aminopyrenyl moieties linked to a triazine ring, in order to reveal the nature of both the electronic excited states and relaxation pathways of the compounds. Our experimental results complement quantum chemical calculations. We propose that the lowest excited state from which fluorescence proceeds is localized on a single individual aminopyrene moiety. In contrast, excitation to a higher excited state is likely followed by a migration of energy to another nearby aminopyrene chromophore before the internal conversion to the emitting state takes place. We suggest that this migration is responsible for the experimentally measured decrease of fluorescence anisotropy of the studied compounds.

Conserved fatty acid profiles and lipid metabolic pathways in a tropical reef fish exposed to ocean warming - An adaptation mechanism of tolerant species?

Climate warming is causing rapid spatial expansion of ocean warm pools from equatorial latitudes towards the subtropics. Sedentary coral reef inhabitants in affected areas will thus be trapped in high temperature regimes, which may become the "new normal". In this study, we used clownfish Amphiprion ocellaris as model organism to study reef fish mechanisms of thermal adaptation and determine how high temperature affects multiple lipid aspects that influence physiology and thermal tolerance. We exposed juvenile fish to two different experimental conditions, implemented over 28 days: average tropical water temperatures (26 °C, control) or average warm pool temperatures (30 °C). We then performed several analyses on fish muscle and liver tissues: i) total lipid content (%), ii) lipid peroxides, iii) fatty acid profiles, iv) lipid metabolic pathways, and v) weight as body condition metric. Results showed that lipid storage capacity in A. ocellaris was not affected by elevated temperature, even in the presence of lipid peroxides in both tissues assessed. Additionally, fatty acid profiles were unresponsive to elevated temperature, and lipid metabolic networks were consequently well conserved. Consistent with these results, we did not observe changes in fish weight at elevated temperature. There were, however, differences in fatty acid profiles between tissue types and over time. Liver showed enhanced α-linolenic and linoleic acid metabolism, which is an important pathway in stress response signaling and modulation on environmental changes. Temporal oscillations in fatty acid profiles are most likely related to intrinsic factors such as growth, which leads to the mobilization of energetic reserves between different tissues throughout time according to organism needs. Based on these results, we propose that the stability of fatty acid profiles and lipid metabolic pathways may be an important thermal adaptation feature of fish exposed to warming environments.

A key metabolic gene for recurrent freshwater colonization and radiation in fishes.

Colonization of new ecological niches has triggered large adaptive radiations. Although some lineages have made use of such opportunities, not all do so. The factors causing this variation among lineages are largely unknown. Here, we show that deficiency in docosahexaenoic acid (DHA), an essential ω-3 fatty acid, can constrain freshwater colonization by marine fishes. Our genomic analyses revealed multiple independent duplications of the fatty acid desaturase gene Fads2 in stickleback lineages that subsequently colonized and radiated in freshwater habitats, but not in close relatives that failed to colonize. Transgenic manipulation of Fads2 in marine stickleback increased their ability to synthesize DHA and survive on DHA-deficient diets. Multiple freshwater ray-finned fishes also show a convergent increase in Fads2 copies, indicating its key role in freshwater colonization.