Developmental and growth dynamics of the vertebral column in farmed Atlantic salmon

It is well known from birds and mammals that skeletal tissues are dynamic and sensitive to factors such as exercise and nutrition. In the present proposal, we wish to elucidate the effects of mechanic stimulation of vertebrae through exercise, and the eff ects of fast growth on vertebral architecture and bone matrix composition in salmon. The effects of artificially induced maximal growth on the vertebrae of both wild and farmed populations will also be studied. Furthermore, we wish to investigate the rela tionship between vertebral bone architecture, matrix composition and strength, as a result of fast growth. Atlantic salmon parr and smolts will be reared under combinations of photoperiod and temperature that generate between a 4 and 6 fold differences in growth rate between experimental groups. Selected individuals from these studies will be transferred to the exercise system (see below) to study the combined effect extreme growth and exercise. The exercise system is supplied with both fresh and salt wat er at different temperatures and the water current can be regulated up to 80 cm per second (i.e. allowing exercise at four body lengths per second for fish up to 20 cm. Salmon in different life stages, and with different growth rates will be tested in the exercise system. Alteration of the environment may lead to dynamic expressional changes in many genes involved in growth regulation and those coding matrix constituents. We are therefore interested in establishing a small micro-array containing about 30 expressed sequence tags (EST). By analyzing the EST data banks provided by Norway (http://www.salmongenome.no/cgi-bin/sgp.cgi) and Canada (http://web.uvic.ca/cbr/grasp/) genes involved in skeletal growth will be selected in addition to those already studi ed in our group. By brief scanning we have already identified a few 'skeletogenic genes' (noggin3, col II, pitx1, pitx2 ) and in addition to already characterized genes (see section molecular regulation of bone growth). About 30 genes will be spotted on a micro-array-plate by help of the micro-array consortium in Norway (http://www.mikromatrise.no/facility/NMC/page/id/66, ref. Professor Ola Myklebost). This method will hopefully elucidates the plasticity of skeletogenic factors related to exercise and fas t growth in both wild and farmed salmon populations.