Fig. 8.

Working model of the behavioral impacts of water depth, gut distention due to feeding, and location of tactile stimulation. P, pressure-sensitive mechanosensory cells; R3b1, neuron in the subesophageal ganglion that is involved in the choice between swimming and crawling; E, elongation network that is a component of both the swim and the crawl central pattern generators (CPGs); C, contraction network that is a component of the crawl CPG. Filled circles indicate inhibitory interactions; filled arrowheads with plus signs indicate excitatory interactions. DA indicates bath-application of dopamine; the X indicates that DA inhibits the pathway to the swim CPG; the DA also activates the crawl CPG (Puhl et al., 2012). Modified from Esch et al. (Esch et al., 2002).