Functional ontogeny of the circulatory system in lower vertebrates

In contrast to mammalian embryos, which develop under maternal protection, most fish and amphibian larvae are free-living and live in the same or at least a similar environment than the adults. The first studies on fish and amphibian embryos revealed, that in the earliest developmental stages the function of the circulatory system is not linked to the requirements of gas exchange, although the tight integration of these two functions is well established for adults. Furthermore, nervous control of the central cardiac system becomes functional only later during development. This project therefore will analyze the functional development of the circulatory system in fish, focusing especially on the development of the linkage between cardiac function and the requirements of gas exchange. A crucial aspect will be the capability of the embryo or larvae for a coordinated response to changes in environmental factors like temperature and oxygen availability, and the impact of these factors on the integration of respiratory and cardiac function. An interesting parameter with respect to the development of the circulatory system will be the capillarization of tissues. The experiments will reveal whether the early onset of cardiac activity and blood glow is important to assure a proper development of the capillary system in tissues. The influence of temperature and oxygen availability on tissue capillarization will also be considered in these experiments. The experiments thus will provide insight into the flexibility of the developing cardiac system in response to changing environmental conditions. For free-living embryos this flexibility might be a crucial parameter for the survival of a species.