The
crustacean hyperglycemic hormone (CHH) family of
peptides includes CHH, moult-inhibiting
hormone (MIH) and mandibular organ-inhibiting
hormone (MOIH). In the crab
Cancer pagurus,
isoforms of these
peptides, as well as CHH precursor-related
peptide (CPRP), have been identified in the X-organ-sinus gland (XO-SG) system. Using
peptides isolated from the C. pagurus SG,
antibodies to each family member and CPRP were generated. These sera were then used to map the distributions and co-localization patterns of these
peptides in the neuroendocrine organs of seven
Cancer species:
Cancer antennarius,
Cancer anthonyi,
Cancer borealis,
Cancer gracilis,
Cancer irroratus,
Cancer magister and
Cancer productus. In addition to the XO-SG, the pericardial organ (PO) and two other neuroendocrine sites contained within the stomatogastric nervous system, the anterior cardiac plexus (ACP) and the anterior commissural organ (ACO), were studied. In all species, the
peptides were found to be differentially distributed between the neuroendocrine sites in conserved patterns: i.e. CHH, CPRP, MIH and MOIH in the XO-SG, CHH, CPRP and MOIH in the PO, and MOIH in the ACP (no immunolabeling was found in the ACO). Moreover, in C. productus (and probably in all species), the
peptides present in the XO-SG and PO were differentially distributed between the neurons within each of these neuroendocrine organs (e.g. CHH and CPRP in one set of XO somata with MIH and MOIH co-localized in a different set of cell bodies). Taken collectively, the differential distributions of CHH family members and CPRP both between and within the neuroendocrine organs of crabs of the genus
Cancer suggests that each of these
peptides may be released into the circulatory system in response to varied, tissue-specific cues and that the PO- and/or ACP-derived
isoforms may possess functions distinct from those classically ascribed to their release from the SG.