The importance of novelty: Male–female interactions among blue-black grassquits in captivity

Mate choice is a primary mechanism driving the evolution of sexually selected traits such as elabo-rate displays and ornaments. In a majority of taxa studied to date, females are seen to actively sampleand evaluate multiple males, presumably to optimize mating opportunities. During this process femalesmay encounter males both familiar and novel, a distinction that might influence how mate choice pro-ceeds. Using a socially monogamous passerine, the blue-black grassquit (Volatinia jacarina), we studiedhow females respond to novel versus familiar (“paired”) males, and how encounters with novel malesinfluence subsequent interactions with their paired males. Additionally, we measured the hormonalresponse of males after visualizing their paired females interacting with novel males. We found thatfemales were attentive to novel males irrespective of these males’ phenotypic attributes, suggesting thatin these interactions novelty is highly relevant. After exposure to novel males, females tended to respondaggressively towards their paired males; by contrast, the behaviour of males towards their paired femalesdid not change. Moreover, we did not detect any hormonal responses of males to viewing their pairedfemales interacting with novel males. Together these results suggest that the distinction between famil-iarity and novelty may hold special relevance for females in mate choice, a finding that bears upon ourunderstanding of the evolution of extra-pair paternity and reproductive behaviour.

Effects of ocean acidification on the swimming ability, development and biochemical responses of sand smelt larvae

Ocean acidification, recognized as a major threat to marine ecosystems, has developed into one of the fastest growing fields of research in marine sciences. Several studies on fish larval stages point to abnormal behaviours, malformations and increased mortality rates as a result of exposure to increased levels of CO2. However, other studies fail to recognize any consequence, suggesting species-specific sensitivity to increased levels of CO2, highlighting the need of further research. In this study we investigated the effects of exposure to elevated pCO2 on behaviour, development, oxidative stress and energy metabolism of sand smelt larvae, Atherina presbyter. Larvae were caught at Arrábida Marine Park (Portugal) and exposed to different pCO2 levels (control: ~600μatm, pH=8.03; medium: ~1000μatm, pH=7.85; high: ~1800μatm, pH=7.64) up to 15days, after which critical swimming speed (Ucrit), morphometric traits and biochemical biomarkers were determined. Measured biomarkers were related with: 1) oxidative stress - superoxide dismutase and catalase enzyme activities, levels of lipid peroxidation and DNA damage, and levels of superoxide anion production; 2) energy metabolism - total carbohydrate levels, electron transport system activity, lactate dehydrogenase and isocitrate dehydrogenase enzyme activities. Swimming speed was not affected by treatment, but exposure to increasing levels of pCO2 leads to higher energetic costs and morphometric changes, with larger larvae in high pCO2 treatment and smaller larvae in medium pCO2 treatment. The efficient antioxidant response capacity and increase in energetic metabolism only registered at the medium pCO2 treatment may indicate that at higher pCO2 levels the capacity of larvae to restore their internal balance can be impaired. Our findings illustrate the need of using multiple approaches to explore the consequences of future pCO2 levels on organisms.