FMRFAMIDE-LIKE IMMUNOREACTIVITY IN THE CENTRAL-NERVOUS-SYSTEM OF THE LANCELET BRANCHIOSTOMA-LANCEOLATUM

The central nervous system of the lancelet Branchiostoma lanceolatum h as been studied immunocytochemically in order to localize FMRFamide-li ke peptides. Immunoreactive neurons are serially disposed along the la teral and ventrolateral zones of the spinal cord, and immunostained pr ocesses connect some of the nerve cell bodies. The same kind of immuno reactivity has been localized in nerve fibers projecting to the dorsal spinal roots, whereas in the so-called ventral roots the neuromuscula r junctions appear to be labeled. Very likely, the immunoreactive nerv e cell bodies are involved in the control of visceral- and somato-moto r neural circuits and FMRFamide-like peptides could play a fundamental role in the transmission of nervous impulses. Moreover, immunofluores cent FMRFamide-like materials are shown by the receptor cells of the H esse eyecups, and they are probably involved in the regulation of ligh t perception. The experimental data suggest that the lancelet has a ve rtebrate-like chemical neuroanatomy with respect to neuropeptides, alt hough its CNS is less advanced in its pattern of regional organization .