The role of the Glucocorticoid Receptor in the Regulation of Diel Rhythmicity.

Virtually all organisms have adapted to the earth's day-night cycles by the evolution of endogenous rhythms that regulate most biological processes. Recent research has highlighted the role of glucocorticoids and the Glucocorticoid receptor (GR) in coordinating clock function across various levels of biological organisation. In the present study, we have explored the role of the GR in the rhythmicity of the biological clock, by comparing 5 day old wildtype zebrafish larvae (gr) with mutant larvae with a non-functional GR (gr).

Profound effects of glucocorticoid resistance on anxiety-related behavior in zebrafish adults but not in larvae.

Previously, adult zebrafish with a mutation in the gene encoding the glucocorticoid receptor (Gr) were demonstrated to display anxiety- and depression-like behavior that could be reversed by treatment with antidepressant drugs, suggesting that this model system could be applied to study novel therapeutic strategies against depression. Subsequent studies with zebrafish larvae from this gr line and a different gr mutant have not confirmed these effects. To investigate this discrepancy, we have analyzed the anxiety-like behavior in 5 dpf gr larvae using a dark/tapping stimulus test and a light/dark preference test.

Reproductive toxicity of primary and secondary microplastics to three cladocerans during chronic exposure.

Microplastics (<5 mm) are distributed ubiquitously in natural environments. The majority of microplastics in aquatic environments are shown to have rough surfaces due to various weathering processes (secondary microplastics; SMP), while laboratory studies predominantly utilise pristine microplastics (primary microplastics; PMP). Here we present the results from a study comparing the chronic effects of pristine PMP and artificially weathered SMP to three different Cladoceran species (Daphnia magna, Daphnia pulex, Ceriodaphnia dubia).

Acute sensitivity of three Cladoceran species to different types of microplastics in combination with thermal stress.

Microplastics (<5 mm, MP) are ubiquitously distributed in the environment, causing increasing concern regarding their potential toxicity to organisms. To date, most research has focussed on the impacts of MPs on marine and estuarine organisms, with fewer studies focussing on the effects of microplastics on freshwater ecosystems, especially under different environmental conditions. In the present study, the sensitivity of two temperate Cladoceran species, Daphnia magna and Daphnia pulex, and a smaller tropical species Ceriodaphnia dubia, to primary microplastics (PMP) and secondary (weathered) microplastics (SMP) was assessed.