Volume Control by Muscle Fibers of the Blue Crab Volume readjustment in hypotonic salines

I N T R O D U C T I O N This study concentrates on a unique volume response of blue crab muscle fibers to hypotonic salines. When single fibers isolated from vertebrate muscle (Reuben et al., 1963; Blinks, 1965) or from invertebrate muscle (Reuben et al., 1964; Gainer and Grundfest, 1968) are placed into hypotonic salines, their volumes usually increase to new steady-state levels which remain constant until the fibers are returned to their control salines (after which they approach their initial volumes). However, when muscle fibers from Callinectes sapidus are placed in hypotonic salines, their volumes increase to new steady-state levels, but then with time spontaneously decrease towards their initial volumes in control salines. Upon return to control salines their volumes fall below their initial values. These volume responses of blue crab muscle fibers to hypotonic salines will be referred to as "volume readjustments." A few other examples of volume readjustment have been reported in the literature. Kitching (1934) found that the protozoan, Cothurnia curvula, occasionally exhibited volume readjustment. Reuben et al. (1963) and Grundfest