Cell Tissue Res (1991) 265:19-33 Cell and Tissue Research 9 Springer-Verlag 1991 Differential distribution of [I-pigment-dispersing hormone (p-PDH)-like immunoreactivity in the stomatogastric nervous system of five species of decapod crustaceans Lawrence I. Mortin* and Eve Marder Biology Department and Center for Complex Systems, Brandeis University, Waltham, MA 02254, USA Accepted February 2, 1991 Summary. Pigment-dispersing hormone (PDH) acts to disperse pigments within the chromatophores of crusta- ceans. Using an antibody raised against ft-PDH from the fiddler crab Uca pugilator, we characterized the dis- tribution of ft-PDH-like immunoreactivity in the stoma- togastric nervous system of five decapod crustaceans: the crabs, Cancer borealis and Cancer antennarius, the lobsters, Panulirus interruptus and Homarus americanus, and the crayfish, Procambarus clarkii. No somata were stained in the stomatogastric ganglion (STG) or the esophageal ganglion in any of these species. Intense PDH-like staining was seen in the neuropil of the STG in P. interruptus only. In all 5 species, cell bodies, pro- cesses, and neuropil within the paired circumesophageal ganglia (CGs) showed PDH-like staining; the pattern of this staining was unique for each species. In each CG, the ft-PDH antibody stained: 1 large cell in C. bor- ealis; 3 small to large cells in C. antennarius; 3-8 medi- um cells in P. clarkii; 1-4 small cells in H. americanus; and 13-17 small cells in P. interruptus. The smallest cell in each CG in C. antennarius sends its axon, via the inferior esophageal nerves, into the opposite CG; this pair of cells, not labeled in the other species studied, may act as bilateral coordinators of sensory or motor function. These diverse staining patterns imply some de- gree of evolutionary diversity among these crustaceans. A ft-PDH-like peptide may act as a neuromodulator of the rhythms produced by the stomatogastric nervous system of decapod crustaceans. Key words: ft-.Pigment-dispersing hormone (ft-PDH) - Ganglia, invertebrate Immunohistochemistry Anti- body staining - Peptide localization - Cancer antennar- ius, Procambarus clarkii, Panulirus interruptus (Crusta- cea) The stomatogastric nervous system of decapod crusta- ceans controls the processing and movement of food * Present address." Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, E25-634, Cambridge, MA 02139, USA Offprint requests to: E. Marder particles through the foregut. At least four different rhythmic motor patterns control the muscles that move, chew, and filter food before its entry into the hindgut (Robertson and Moulins 1981). Central pattern genera- tors (CPGs) within this part of the central nervous sys- tem (CNS) produce these rhythmic motor patterns (see Selverston and Moulins 1987). The neurons, synaptic connections, and mechanisms for rhythm production for two of these CPGs have been well characterized (Selver- ston and Moulins 1987). This preparation has proven to be an excellent model system for studying the effects of neuromodulators on well-defined neural circuits (see Marder 1987; Harris-Warrick 1988). Numerous peptides have been identified as modulators of the rhythms of the stomatogastric nervous system, including proctolin (Hooper and Marder 1984, 1987; Marder etal. 1986; Heinzel and Selverston 1988; Dickinson and Marder 1989), FMRFamide-like peptides (Hooper and Marder 1984; Marder et al. 1987; Weimann and Marder 1989), and a cholecystokinin-like (CCK-like) peptide (Turri- giano and Selverston 1989, 1990). The peptides, pigment-dispersing hormone (PDH) and red pigment-concentrating hormone (RPCH), act to disperse and concentrate pigments, respectively, with- in the chromatophores of crustaceans (Rao 1985). RPCH is distributed widely in the stomatogastric ner- vous system of the crab Cancer borealis (Nusbaum and Marder 1988) and the lobster Panulirus interruptus (Dickinson and Marder 1989). This distribution is corre- lated with the functional modulation of several of the rhythms produced by this part of the crustacean CNS in response to application of exogenous RPCH (Nus- baum and Marder 1988; Dickinson and Marder 1989; Dickinson et al. 1990). Originally, PDH was called distal retinal pigment hormone (DRPH) as it was identified based on its ability to produce light-adapting movements of pigments within the crustacean retina (Kleinholz 1936). DRPH was first isolated and sequenced from the eyestalks of the shrimp Pandalus borealis (Fernlund 1976). Experiments on ex- tracts from crustacean eyestalks demonstrated the ex- istence of a melanophore-dispersing hormone (MDH) that darkened the body of several crustacean species by