Visiting Professor in USC’s Manahan Lab
Professor of Physiology
Department GAFFA, Faculty of Science and Technology
University of Basque Country (UPV/EHU)
Spain
Physiological mechanisms underlying differential growth in size-segregated spat groups of marine bivalves
Tuesday, October 2
12 PM
AHF 153 (Torrey Webb Room)
Abstract: Rates of growth are highly variable in bivalve mollusks and much of this is genetically controlled. Aquaculture practices, through the artificial selection for faster growth, have brought out differentiated growth phenotypes, enabling experiments to investigate the physiological mechanisms underlying this differential expression of growth rate. Persistent physiological differences reported among these groups contrast with the flexible behavior for feeding and growth traits required to cope with changes in the food environment (phenotypic plasticity). From this perspective, the specific aims of our research were to (i) assess the extent to which physiological behavior accounting for growth performance is endogenously (genetically) determined, and (ii) to question how much of this behavior can be environmentally modulated to achieve a more effective exploitation of available food resources within the limits set by the genetic constitution of individuals.
We addressed these issues with different species of bivalves by using groups of spat from a given generation that were artificially segregated on the basis of size in order to produce two differentiated growth categories or groups, henceforth F and S for fast and slow growers, respectively. These groups were subsequently subjected to different food rations to produce growth rate variation in the laboratory while physiological components of the energy balance were determined. Both F and S phenotypes exhibited the same pattern of response and a similar capacity to compensate for variations in food availability through both short and long-term adjustments of feeding behavior which optimized food acquisition. However, phenotypic plasticity does not include constitutive differences in the physiological behavior that underlies the differential growth between F and S phenotypes maintained throughout the dietary conditions. Under standard (hatchery) feeding conditions, the faster growth of F phenotype is achieved through a combination of faster feeding (assisted by larger gills) and an increased metabolic efficiency which results in reduced unitary costs of growth. For F and S groups segregated under restrictive feeding conditions, however, fast growth appears to rely mainly on energy saving mechanisms based on reduced metabolic costs of body maintenance.
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