different stages in the life cycle and to evolve specialised forms to go with them. This strategy is widely used — from the adult mayfly whose sole task it is to find a mate, to the ever-hungry caterpillar — and involves often dramatic bodily transformations between stages. Before the term 'life history' was even coined, such metamorphoses — like the tadpole turning into a frog illustrated on t...

In his book on behavioural endocrinology, Randy Nelson describes 'stress' as a 'notoriously ethereal concept'. Yet, despite this lack of clarity, studies of the consequences of stress across different time scales, life history stages, taxa and levels of biological enquiry form a large part of modern biology and biomedicine. Organisms need to recognise and respond to environmental challenges. Be...

the age and growth of the persian sturgeon, acipenser persicus, obtained from the iranian coastal waters of the caspian sea, were studied through analysis of the pectoral fin ray section from 180 specimens, ranging in fork length (fl) from 66 to 203 cm. the specimens were obtained from commercial fisheries between october 2008 and june 2010. interpretation of growth bands in the pectoral fin ra...