Fast-twitch muscle fibers from juvenile blue crabs (left) have "normal" cellular dimensions (100 um or less) while cells from adults (right) have giant cells (>500 um). Therefore, as crustaceans develop, their fibers "become giant", which presents problems of a low surface area to volume ratio (SAV), and long intracellular diffusion distances (from Boyle et al. 2003).

Mitochondrial redistribution associated with increase in Blue crab fast-twitch fiber diameter (white dots mark individual mitochondria). Small cells from juvenile crabs have mitochondria distributed at the sarcolemmal membrane (panel A) and in the fiber interior (panel B). In contrast, large cells from adults have shifted all of the oxidative potential to the cell periphery (panel E), and very few mitochondria are found in the fiber core (panel F) (from Boyle et al. 2003).

The differences in SAV (left) and the time for metabolites to diffuse between mitochondria (right) in the small cells of juvenile and the large cells of adult Blue crabs. During development, Blue crabs must deal with the increasing effects of reduced SAV and increased diffusion time.