Why the location and quality of food sources in the soil are sometimes likely to stimulate random movements by C. Elegans, but at other times are more likely to stimulate directed movements.

The Caenorhabditis elegans dauer state is a hibernation-like state of diapause that displays a dramatic reduction in spontaneous locomotion.

Explanation:

Mutations affecting the neurotransmitter dopamine, which regulates voluntary movement in many organisms, can stimulate movement in dauers. The movement of quiescent animals is stimulated by conditions that reduce dopamine signaling and also by conditions predicted to increase dopamine signaling. The stimulation of movement by increased dopamine is much more pronounced in quiescent daf-2 (-) dauer and dauer-like adult animals.

In C. elegans hermaphrodites, dopamine is produced by eight neurons and signals via at least four dopamine receptors, DOP-1 through DOP-4. In addition, a presynaptic reuptake transporter, DAT-1, removes dopamine from the extracellular space to terminate signaling. In C. elegans, dopamine is best known for mediating the "basal slowing response" in which the animal's movement slows when it encounters food ... Dopamine is thought to be released in response to food and to act on motor neurons to modulate the animal's movement. Animals that cannot produce dopamine fail to slow in response to food and exogenous dopamine slows the movement of animals cultured without food. The response to dopamine in this situation is complex, as the absence of specific dopamine receptors can have either positive or negative effects on movement.