The increase or decrease in solute concentrations outside of an organism can result in a stress response, which can include changes in behavior or gene expression. As an animal that is hyperosmotic to its normal environment, C. elegans exhibits structures and mechanisms to assess and deal with changes in the osmolarity of its environment. On a behavioral level, C. elegans avoids regions of high osmolarity. On a physiological level, hypertonic stress results in the upregulation of glycerol 3-phosphate dehydrogenases,
gpdh-1 (strong) and
gpdh-2 (weak). These genes aid in adapting to hypertonic environments by adjusting glycerol concentrations within cells.