Distribution of FMRF-amide-like peptide in the nervous system of a mermithid nematode, Romanomermis culicivorax.

The nervous system of the mermithid nematode Romanomermis culicivorax was investigated at different developmental stages for the distribution of the neuropeptide FMRF-amide. An FMRF-amide-like peptide was detected by an indirect immunofluorescence technique. The peptidergic nervous system increased in complexity during development. In adults, FMRF-amide-like peptide was present in the nerve ring, cephalic papillary ganglia, cephalic nerves, amphids, ganglia posterior to the nerve ring, longitudinal nerve cords and several mid-body region ganglia. The distribution of peptidergic ganglia in the tail region was different for each sex. Four clusters of ganglia were present in the tail of females, whereas such ganglia were absent in the tail of males. The results suggest that FMRF-amide-like peptide is widely distributed within the nervous system of R. culicivorax and might function as a neurohormone or neurotransmitter in controlling physiological and developmental processes.