PATTERNS AND PROJECTIONS OF CRUSTACEAN CARDIOACTIVE-PEPTIDE-IMMUNOREACTIVE NEURONS OF THE TERMINAL GANGLION OF CRAYFISH

Three distinct clusters of crustacean cardioactive-peptide-immunoreact ive neurones occur in the terminal abdominal ganglion of the crayfish species Orconectes limosus, Astacus leptodactylus, Astacus astacus and Procambarus clarkii, as revealed by immunocytochemistry of whole-moun t preparations and sections. They exhibit similar topology and project ion patterns in all four studied species. An anterior ventral lateral and a posterior lateral cluster contain one small, strongly stained pe rikaryon and two large, less intensely stained perikarya, each showing contralateral projections. A posterior medial lateral cluster of up t o six cells also contains these two types of perikarya. Whereas the sm all type perikarya belong to putative interneurones, the large type pe rikarya give rise to extensive neurohaemal plexuses in perineural shea ths of the third roots of the fifth abdominal ganglia, the connectives , the dorsal telson nerves, the ganglion itself, its roots and arterio lar supply. Thin fibres from these plexuses reach newly discovered put ative neurohaemal areas around the hindgut and anus via the intestinal and the anal nerves, and directly innervate the phasic telson muscula ture. A comparison with earlier investigations of motoneurones and seg mentation indicates that these three cell groups containing putative n eurosecretory neurones may be members of at least three neuromeres in this ganglion. Crustacean cardioactive peptide released from these neu rones may participate in the neurohumoral and modulatory control of di fferent neuronal and muscle targets, thereby exceeding its previously established hindgut and heart excitatory effects.