Dopaminergic neurons in free-living Rhabditid nematodes. A. Schematic of C. elegans head showing dopaminergic (DA) neurons on one side; each neuron has a bilaterally symmetric partner. CEPD: dorsal cephalic neuron; CEPV: ventral cephalic neuron; ADE: anterior deirid neuron. In all images, anterior is to the left, and dorsal up (except as noted). B. FIF-treated C. elegans larval head showing DA neurons (dorsoventral view) on right and left sides. C. PDE (posterior deirid neuron) neuron in lateral, mid-posterior body wall of C. elegans treated with 5HTP and stained with anti-serotonin (TRITC-conjugated secondary antibody). A dorsally directed dendrite arises from the soma: an axon extends ventrally and projects within the ventral nerve cord. D. Schematic of C. elegans body showing locations of DA neurons, including the PDE. Only the somata are shown for the head DA neurons. E-J. Dopaminergic neurons in species we examined, revealed by FIF and immunofluoresence. The pattern of DA cells in C. briggsae is identical to that of C. elegans (data not shown). Column 1 (FIF Head): FIF-treated worm heads. Slender-headed arrows indicate presumptive CEPD and CEPV homologs (in F-J, abbreviated D or V). Broad arrowheads indicate presumptive ADE homologs. In some panels both right and left cells can be seen (more than one arrow). Column 2 (+5HTP ADE): Putative ADE homologs visualized with anti-serotonin in 5HTP-treated worms (somata indicated with arrow). Soma locations and processes are quite similar to those in C. elegans, although many ADE posterior-directed neurites leading to commissures are longer than illustrated for C. elegans. Some panels are montages of nearby planes of focus to better show the cell morphology. Column 3 (FIF PDE): Lateral, mid-posterior body wall of FIF-treated worms showing somata of likely PDE homologs (arrow); in some panels both right and left cells can be seen (more than one arrow). Strong gut fluorescence often makes PDEs difficult or impossible to see by FIF. Column 4 (+5HTP PDE): PDE homologs in body wall visualized with anti-serotonin in 5HTP-treated worms (soma indicated by arrow); in some panels both right and left cells can be seen (more than one arrow), although sometimes the soma is out of the plane of focus. E. Caenorhabditis sp. 3 (PS1010). F. Oschieus myriophila (DF52020). G. Pellioditis typica (DF5025). Panel G3 (FIF PDE) is a ventral view showing both left and right PDE somata. H. Rhabditella axei (DF5006). Panel H4 (+5HTP PDE) is a ventral view in which both left and right cells can be seen. I. Pristionchus pacificus (PS312). In panel I4 (+5HTP PDE), note the long anteriorly directed PDE dendrite. J. Panagrellus redivivus (PS1163).