Effects of prenatal stress on the early development of behaviour and cognitive capabilities: a comparative approach – PReSTO'Cog

The diversity of the animal models used in PReSTO Cog, from marine invertebrate (cutlefish) to fish (truits and zebrafish) birds (quails and fowl) implied an approach highly comparative. More, the species studied in the present project differ from each other in term of domestication levels. In each species, effects of « artificial » stressor will be compared to those of « natural » stressor. This will allow PReSTO’Cog to tackle both proximate (mecanisms) and ultimate (function, evolution) questions about effects of prenatal stress.

Based on the first series of experiments, prenatal stress induces behavioural and/or morphological changes in hatchlings of all species of the project. Effects depends on the kind of stress applied to the embryo (artificial or natural). Behavioural phenotype of birds (chicks and quail chicks), and cuttlefish seems more sensitive to maternal and artificial stress. These differential effects are attenuated in truits while maternal, artificial and natural stress have the same effect change in juveniles of zebra fish.

The results of the running studies (on physiology, cognition and brain) will refine the results described above. Indeed, Behavioural changing can help to compensate physiological déséquilibres while, in contrast neurophysiological or endocrin processes can regulate behavioural perturbations induced by prnata stress.
Completion of this project will be necessary to accurately evaluate the application work out of PReSTO’Cog. (understanding of meccanisms involved, application to aquaculture and to welfare of species of interest).

After completing the design of both material and human structures in each partner, the consortium is presently working on data acquisition and analysis. At this stage (18 months) the project has been valorised by 8 international communication, 7 national communications. Two symposia were devoted to the prenatal stress have been organised by partnairs of the consortium (one in France, one in Australia). These symposia involved the greatest specialist of the field at an international level. A significant effort was made to communicate the project, its aims and first results to the public, through a national radio (France Inter) advertising and several national conferences. Each partnair was involved actively in these valorisation processes.

PReSTO’Cog aims at examining the effects of natural or artificial embryonic and maternal stress on early behaviours, neuroendocrine system and brain plasticity of early juveniles. This project gathers together five research units from French Universities, CNRS, INRA and IFREMER for a total of 14 researchers and 9 technicians who are highly complementary both in their discipline (ethology, endocrinology and neurobiology) and in their technical skills. Prenatal stress (PS) was subject to a spectacular scientific interest in the last two decades and led to several societal issues applied in human health, in animal welfare regulations, in ecology and in basic research in developmental psychobiology. PReSTO’Cog proposes to study PS in innovative animal models: cephalopod (cuttlefish), fishes (zebrafish and trout) and birds (quails and hens). These animal models are all oviparous. There is no parental care to eggs in cuttlefish, trout and zebrafish while bird’s eggs can be kept in artificial incubators. This allows a direct access to embryos and a rigorous control of the embryonic sensory experience. Animal species in this project are all precocial (i.e. hatchlings are autonomous), so that analysis of juvenile behaviours from hatching is possible, without any bias nor interference with maternal care.

Basically, PReSTO’Cog tackles two fundamental questions that are still unresolved or under sharp debate:
1- Does PS have positive or negative effects on adaptive behaviours of juveniles?
2- Does the nature (e.g. natural or artificial) of the stressor applied directly to embryo modify those effects of the PS?
An additional, but crucial issue will be addressed in this project:
3- Does stress applied to mothers induce the appearance of similar PS phenotype in their offspring? If so, what are the potential mechanisms of such intergenerational influence?

To address these questions, different models were carefully chosen, from invertebrates to vertebrates, poïkilotherms to homeotherms and from wild to more or less domesticated.
Natural stressors are stimuli that embryos can experience in natural conditions (predator odour, distress calls…). Artificial stressors can potentially be met in breeding conditions (handling, exposure to aversive chemicals…). To investigate any maternal effect, chronic stressor will be applied to females before spawning. Endocrine studies will be led to give rise to any physiological response of embryos and juveniles to prenatal or maternal stress.

In hatchlings of each species, adaptive skills will be assessed by testing defensive, exploratory and/or feeding behaviours. In gregarious species, some early social behaviours will also be investigated. In addition to this behavioural part, embryonic learning capacities will also be examined in this project. In parallel possible effects of PS on brain development will be appraised.

Comparative studies of species that are very different from each other are highly challenging. But these models are characterized by well known and monitorable embryonic development and precocial hatchlings so that the outputs of PReSTO’Cog, obtained in a “simplified scenario” would be broaden to a wide range of animal species.