2022-10-20, Rakel, Kim, Becker, Denis, Bussen, Dino, Classen, Silke, Preuss, Thomas, Strauss, Tido, Zenker, Armin, Gergs, André

In chemical risk assessment, extrapolations from laboratory tests to more realistic conditions are essential to address the toxic effects of pesticides on individuals and populations under field conditions. To transfer toxicological laboratory tests to differing temperature conditions, or outdoor field scenarios, the consideration of temperature dependence is essential and increases realism. Special consideration is given to the impact of temperature on direct sensitivity of organisms to pesticides, for which there are only few modelling approaches available so far. We present a concept for applying physiological temperature dependencies to toxicokinetic–toxicodynamic (TKTD) parameters in the General Uniformed Threshold model of Survival (GUTS). To test this approach in an exemplary study, temperature dependencies from studies on the developmental rate of the mayfly Cloeon dipterum were applied to the parameters of a previously parameterised TKTD model of this species after exposure to imidacloprid. Using a physiologically derived temperature correction for the TKTD rate constants, model predictions for independently conducted toxicology experiments with temperature ranges between 7.8 and 26.4 °C were performed for validation. Our approach demonstrates the successful transfer of a physiological observed temperature dependency on toxicity parameters and survival patterns for Cloeon dipterum and imidacloprid as a case study.

2018-11, Yan, Lu, Zenker, Armin, Suter-Dick, Laura

2020-09-25, King, Alex, Zenker, Armin, Gut, Michelle

In contrast to established zebrafish gene annotations, the question of sex determination has still not been conclusively clarified for developing zebrafish, Danio rerio, larvae, 28 dpf or earlier. Recent studies indicate polygenic sex determination (PSD), with the genes being distributed throughout the genome. Early genetic markers of sex in zebrafish help unravel co-founding sex-related differences to apply to human health and environmental toxicity studies. A qPCR-based method was developed for six genes: cytochrome P450, family 17, subfamily A, polypeptide 1 (cyp17a1); cytochrome P450, family 19, subfam-ily A, polypeptide 1a (cyp19a1a); cytochrome P450, family 19, subfamily A, polypeptides 1b (cyp19a1b); vitellogenin 1 (vtg1); nuclear receptor subfamily 0, group B, member 1 (nr0b1), sry (sex-determining region Y)-box 9b (sox9b) and actin, beta 1 (actb1), the reference gene. Sry-box 9a (Sox9a), insulin-like growth factor 3 (igf3) and double sex and mab-3 related transcription factor 1 (dmrt1), which are also known to be associated with sex determination, were used in gene expression tests. Additionally, Next-Generation-Sequencing (NGS) sequenced the genome of two adult female and male and two juve-niles. PCR analysis of adult zebrafish revealed sex-specific expression of cyp17a1, cyp19a1a, vtg1, igf3 and dmrt1, the first four strongly expressed in female zebrafish and the last one highly expressed in male conspecifics. From NGS, nine female and four male-fated genes were selected as novel for assessing zebrafish sex, 28 dpf. Differences in transcriptomes allowed allocation of sex-specific genes also expressed in juvenile zebrafish

2020-06-04, Krieg, Raphael, Zenker, Armin

Invasive non-indigenous crayfish species (NICS) are a global threat to local flora and fauna. Total eradication of an entire population of invasive NICS is a difficult task; several methods have been tested and are still being used, with varying success. Most methods reduce population size and control the species within the targeted area but do not majorly prevent further spread of NICS. However, construction of crayfish barriers can stop the spread of NICS and can therefore, be used to protect indigenous crayfish species (ICS). There are currently very few published scientific papers about this topic. This review reflects current knowledge on how to stop migration when NICS are established and provides useful information for the construction of barriers. The most important findings related to building a crayfish barrier are: the need for a vertical wall with an overhanging lip above the water surface; smooth sections to prevent crayfish from walking or climbing over the obstacle, combined with flow velocities of 0.65 m/s act as a barrier within the waterbody. Additionally, modifications to existing structures, bridges, culverts and dams reduce costs and increase effectiveness in stopping upstream migration of NICS. Barriers can negatively impact certain aquatic species, mainly benthic and slow swimming fish by preventing their migration and genetic exchange. However, they can have positive impacts for ICS and other indigenous organisms against the negative effects of NICS. Local legislation should support barrier construction to prevent the spread of invasive crayfish and other aquatic invaders to protect ark sites for ICS.