The neuroendocrinology of Mytilus edulis

Abstract

The nervous system of the mussel ( Mytilus edulis) comprises three pairs of ganglia. These ganglia, especially the cerebral ganglia, contain large numbers of neurosecretory cells, as demonstrated by histological techniques. The rôle played by the nervous ganglia in the control of reproduction has been demonstrated by organ culture experiments where mantle pieces have been cultured in the presence of the ganglia. Many problems are posed, however, in the quantitative study of the neuroendocrinology of the mussel, and until recently little progress had been made in the purification and characterization of neurohormones. The ablation of the nervous ganglia is impractical and the injection of active substances into the open circulatory system in vivo gives unreproducible results. These problems have been overcome by the use of enzymatically dispersed cell suspensions. These cell suspensions form the basis of a number of rapid and homogenous bioassays for endogenous hormones secreted by the nervous ganglia. To date, a number of putative neurohormones have been demonstrated and are currently being purified: 1. -1: a gonial mitosis-stimulating factor 2. -2: a protein-synthesis-stimulating factor with a growth-hormone like action 3. -3: a glycogen-mobilization hormone and a glycogen-synthesis-stimulating factor that regulate the glycogen storage metabolism linked to the reproductive effort. In addition, the utilization of vertebrate peptide-specific antibodies has revealed the existence of neurosecretory cells containing analogues of these peptides (somatostatin, CCK, FMRFamide, αMSH). The physiological rôle of these peptides remains to be elucidated.