Parental stress and its effects on the offspring of guppies (Poecilia reticulata) and zebrafish (Danio rerio)

Parental stress, either in the context of pregnancy or pre-conception, is increasingly recognised as a contributing factor to offspring disease risk. While the majority of data on the effects of parental stress derive from epidemiology and rodent models, small teleost fish are potentially useful models in which to study these processes. Following an introduction to the relevant concepts (Chapter 1), the subsequent experimental chapters concern two modes of parental stress and their phenotypic influences on the offspring in two different model teleosts: maternal gestational stress in guppies (Chapter 2), and paternal pre-conception stress in zebrafish (Chapter 3).
Chapter 2 focuses on the effects of maternal stress during the gestation period of guppies on the phenotypic characteristics (growth, behaviour, and stress responses) of the offspring. Mothers stressed during gestation produced offspring which grew more slowly during the early postnatal growth period and appeared to show a weakened stress response in adulthood. However, stress also shortened the mother’s gestation period, and therefore subsequent phenotypic alterations in the offspring were likely resultant from shorter intrauterine development time.
Turning to the zebrafish, Chapter 3 Addresses the question of whether paternal stress has intergenerational effects on offspring phenotypes. The work revealed that behavioural and endocrine stress responses were ameliorated in the offspring of fathers exposed to chronic stress, concordant with similar findings from rodent models. It further demonstrated that an intergenerational effect on stress response can be transmitted following remarkably few exposures to a stressful stimulus in the paternal generation, suggesting that zebrafish are particularly sensitive to paternal intergenerational effects.
Following the discovery of paternal intergenerational effects of stress in zebrafish, Chapter 4 details the successful development of a method for isolating high-quality RNA from zebrafish spermatozoa. The chapter lays the groundwork for potential future experiments to investigate a hypothesised RNA-mediated mechanism of epigenetic inheritance – ideas which are expanded on in the general discussion (Chapter 5).