Taurine-like Immunoreactivity in the Motor Nerve Net of the Jellyfish Cyanea capillata.

Two antisera against the sulfonated amino acid taurine were applied to subumbrella tissue of the jellyfish Cyanea capillata. Taurine-immunoreactive nerve nets were found in both the ectoderm and endoderm. The ectoderm had two morphologically and immunocytochemically distinct populations of neurons, the motor nerve net (MNN), which was immunoreactive to the taurine-like molecule, and the diffuse nerve net (DNN), which was immunoreactive to the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide). In the endoderm, immunoreactivity was found in the endodermal DNN. This localization was confirmed by double-labeling experiments, which also revealed that the endodermal DNN neurons may contain both taurine and FMRFamide-related peptide. The presence of a taurine immunoreactivity in the MNN supports the hypothesis that taurine or some chemically related compound is the neurotransmitter at synapses within the MNN of Cyanea.