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

ABSTRACT

The central nervous system of the lancelet Branchiostoma lanceolatum has been studied immunocytochemically in order to localize FMRFamide-like peptides. Immunoreactive neurons are serially disposed along the lateral and ventrolateral zones of the spinal cord, and immunostained processes connect some of the nerve cell bodies. The same kind of immunoreactivity has been localized in nerve fibers projecting to the dorsal spinal roots, whereas in the so-called ventral roots the neuromuscular junctions appear to be labeled. Very likely, the immunoreactive nerve cell bodies are involved in the control of visceral—and somato-motor neural circuits and FMRFamide-like peptides could play a fundamental role in the transmission of nervous impulses. Moreover, immunofluorescent FMRFamide-like materials are shown by the receptor cells of the Hesse eyecups, and they are probably involved in the regulation of light perception. The experimental data suggest that the lancelet has a vertebrate-like chemical neuroanatomy with respect to neuropeptides, although its CNS is less advanced in its pattern of regional organization.