The aging of microplastics in the environment changes their physicochemical properties. While this may affect their toxicity, comparative data on the effects of aged compared to pristine microplastics are scarce. One of those aging processes is the sorption of chemicals, which has mainly been studied for individual pollutants present in marine ecosystems. To investigate how the sorption of a complex mixture of freshwater pollutants affects the toxicity of microplastics, we incubated irregular polystyrene particles (≤63 μm) in either wastewater or ultrapure water. We exposed Daphnia magna to these aged microplastics and their pristine counterparts (80, 400, 2000, and 10,000 particles mL –1 ) over four generations using food limitation as an additional, environmentally realistic stressor. Both particle types affect the survival, reproduction, adult and neonate body lengths, and growth. An exposure to pristine microplastics results in the extinction of the third generation of daphnids. In contrast, wastewater-incubated particles induced a lower mortality. The incubation with wastewater does not change the microplastics’ size, surface charge, and structure. Consistent with the literature, we assume that the adsorption of dissolved organic matter is a key aging process reducing the toxicity of microplastics. Consequently, toxicity testing using pristine microplastics may overestimate the effects of plastic particles in nature.

13Consistent individual differences in behaviour (animal personality) are widespread throughout 14 the Animal Kingdom. This includes variation in risk-taking versus risk-averse behavioural 15 tendencies. Variation in several personality dimensions is associated with distinct fitness 16 consequences and thus, may become a target of natural and/or sexual selection. However, the 17 link between animal personality and mate choice-as a major component of sexual 18 selection-remains understudied. We asked (1) whether females and males of the livebearing 19fish Poecilia mexicana prefer risk-taking mating partners (directional mating preference), (2) 20 or if their preferences are dependent on the choosing individual's own personality type 21 (assortative mating). We characterized each test subject for its risk-taking behaviour, assessed 22as the time to emerge from shelter and enter an unknown area. In dichotomous association 23 preference tests, we offered two potential mating partners that differed in risk-taking 24 behaviour but were matched for other phenotypic traits (body size, shape, and colouration). 25Females, but not males, exhibited a strong directional preference for risk-taking over risk-26 averse mating partners. At the same time, the strength of females' preferences correlated 27 positively with their own risk-taking scores. Our study is the first to demonstrate that a strong 28 overall preference for risk-taking mating partners does not preclude effects of choosing 29 individuals' own personality type on (subtle) individual variation in mating preferences. More 30 generally, two different preferences functions appear to interact to determine the outcome of 31 individual mate choice decisions. 32 33 Plath, M. (2014). Social network analysis resolves 341 temporal dynamics of male dominance relationships. Behavioral Ecology and Sociobiology 68, 935-945. (

Consistent individual differences in behaviour (animal personality) are widespread throughout the Animal Kingdom. This includes variation in risk-taking versus risk-averse behavioural tendencies. Variation in several personality dimensions is associated with distinct fitness consequences and thus, may become a target of natural and/or sexual selection. However, the link between animal personality and mate choice-as a major component of sexual selection-remains understudied. We asked (1) whether females and males of the livebearing fish Poecilia mexicana prefer risk-taking mating partners (directional mating preference), (2) or if their preferences are dependent on the choosing individual's own personality type (assortative mating). We characterized each test subject for its risk-taking behaviour, assessed as the time to emerge from shelter and enter an unknown area. In dichotomous association preference tests, we offered two potential mating partners that differed in risk-taking behaviour but were matched for other phenotypic traits (body size, shape, and colouration).Females, but not males, exhibited a strong directional preference for risk-taking over riskaverse mating partners. At the same time, the strength of females' preferences correlated positively with their own risk-taking scores. Our study is the first to demonstrate that a strong overall preference for risk-taking mating partners does not preclude effects of choosing individuals' own personality type on (subtle) individual variation in mating preferences. More generally, two different preferences functions appear to interact to determine the outcome of individual mate choice decisions.