MATE · MATERNAL EFFECTS: FROM ENVIRONMENT THROUGH TO THE MOLECULAR AND INDIVIDUAL LEVEL, AND BACK TO POPULATION ECOLOGY

MATERNAL EFFECTS: FROM ENVIRONMENT THROUGH TO THE MOLECULAR AND INDIVIDUAL LEVEL, AND BACK TO POPULATION ECOLOGY

A major issue in ecology is to understand the causes of variations in species abundance. In recent years, it has become evident that to address this subject, research must be focused on processes occurring at the level of individuals. In nature, as in human societies, the conditions experienced by individuals can affect their performance later in life. In humans, the foetal environment can affect the intelligence and propensity to obesity of sons and daughters; these effects can be further transmitted to grandchildren. Social conditions experienced by children affect their behaviour later in life. Similar processes take place in nature: for example, maternal food conditions can affect the size of juvenile stages in many animals. Size is important because it affects the chances of capturing food and escaping from predators. In recent years investigations have shown that changes in traits of organisms such as body size can have important consequences for natural populations. In this project, we studied how maternal variation and environmental conditions experienced by embryos affected the performance of larval stages of the shore crab Carcinus maenas. This crab is widespread along the coast of Europe; both females carrying embryos and larvae experience variations in conditions of temperature and salinity that characterise the coastal zones. The project evaluated the effect of temperature and salinity at different levels of organization. At the individual level, developmental rates and body mass were determined. At the biochemical level, variations in lipid classes and fatty acids were measured: lipids are a key energy source in marine animals in general and in crustacean larvae in particular. At the molecular level, responses were evaluated as the level of mRNA expression of genes involved in adaptive responses to environmental stress. Therefore the project used tools and concepts developed in molecular biology, biochemistry and life history theory. Initially, we thought that embryos would be resilient to wide variations of salinity but we discovered that this was not the case. Unexpected results were finding that embryonic development success in nature depends on the present of a copepod parasite that consumes the eggs and at the same time attaches its own eggs within the Carcinus maenas ovigerous mass. We found that in summer, eggs are highly parasitized and females allocate a lower amount of reserves per egg than in autumn when the ovigerous mass are not parasitized. In summer, larvae show lower carbon content and a lower proportion of neutral lipids than in autumn. We also found that variations in allocation of reserves into larvae affect larval survival. Therefore, the combination of parasitism and allocation of reserves should affect the number of individuals completing the larval phase. Neither salinity nor temperature experienced by embryos affected larval body mass. However, we found that salinity conditions experienced by embryos resulted in adaptive responses in gene expression of proteins (i.e. mRNA of Na+-K+-ATPase and Na+-K+-2Cl--cotransporter) involved in the process of osmoregulation. This increment should protect larvae from moderate salinity stress. In summary, larval performance and survival result from complex responses to parasitism, allocation of reserves per egg and molecular responses to salinity. Therefore, in this marine crab, the habitat quality of the embryos is important to explain the quality and the performance of its larval stages.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз