CRUSTACEAN CARDIOACTIVE PEPTIDE-IMMUNOREACTIVE NEURONS IN THE VENTRALNERVOUS-SYSTEM OF CRAYFISH

Crustacean cardioactive peptide-immunoreactive neurons have been mappe d in wholemount preparations and sections of the ventral nervous syste m of the crayfish Astacus astacus and Orconectes limosus. Based on the ir morphology, projection patterns, and staining characteristics, two types of contralaterally projecting neurons are individually identifia ble. In both species, these neurons occur in all neuromers as apparent serial homologs. In adult specimens, one type of cell has a small, de nsely stained dorsal lateral perikaryon, and a descending axon, and ap pears to be an interneuron. Each neuromer contains a single pair of th ese cells. Only in maxillary ganglia, these cells may have an addition al ascending projection. The other type, a neurosecretory cell, has a larger, weakly stained perikaryon and a projection to the segmental th ird root of the next anterior neuromer. Ah neuromers contain a single pair of these neurons adjacent to the interneurons except for the abdo minal neuromers, which contain two pairs of the neurosecretory cells. Central arborizations and varicose processes toward the surface of the third roots and within the perineural sheath of the ventral nerve cor d arise from these neurons. Electron microscopy of granule-containing terminals substantiated that these newly discovered extensive neurohem al areas are release sites for the peptide. In young immature specimen s, the perikarya of both neuron types do not differ in size. Additiona l weakly stained small perikarya occur in all neuromers of Astacus ast acus. These two types of crayfish neurons and other comparable aminerg ic and peptidergic neurons of crayfish and lobster are differentially distributed in the ventral cord. Furthermore, comparison of similar ne uron types in crab, locust, meal worm, and moth species indicates intr a- and interphyletic structural homologies. (C) 1994 Wiley-Liss, Inc.