Synaptic and septate neuromuscular junctions in embryonic lobster muscle

Abstract

IT is generally accepted that there is not enough genetic material to programme uniquely the structure of each neurone in multicellular animals. This then presents the problem of determining how a growing neurone finds and identifies the correct postsynaptic structures. Work on the visual system of Daphnia has demonstrated that the primary sensory neurones form transient gap junctions with undifferentiated neuroblasts in the optic lamina¹. No similar work has been reported for interneurones or motor neurones, however. For instance, we do not know how developing motor neurones find the proper muscle in the periphery². I studied neuromuscular development in lobster embryos and report here that motor neurones form septate junctions with developing muscle cells in the abdomen. In addition, mature neuromuscular synapses are present in the embryo as early as the third to fourth month of the total 9 month development.