Visualization of amphid neuron morphology in various nematodes using DiI staining. (A-E) Morphology of the different amphid neurons was similar in most species. In Caenorhabditis elegans, Caenorhabditis briggsae and Caenorhabditis sp. 3, all the amphid neurons were stained brightly. Cruznema tripartitum did not have any uptake in the ASH and AWB neurons and Pristionchus pacificus also exhibited a relatively weak staining in the ASH neuron and Panagrellus redivivus also had weak uptake in the ASJ and AWB neurons. For each species, the arrowheads indicate the neuronal cell bodies of the different amphids. The smaller arrows indicate the nerve ring as stained by the dye. The larger arrow depicts the dendritic processes that the neurons extend to the exterior. The small letters a and p represent the anterior and posterior regions of the nematode.