Neurosecretory endings associated with striated muscles in three insects (Schistocerca,Carausius, and Phormia) and a frog (Rana)

Summary Neurosecretory nerve-endings are found in association with the ventral longitudinal muscles of the body wall in locust, stick insect and blowfly larva, and with toe muscles in the frog. In the stick insect the endings are less intimately associated with the muscles than in the locust or in the blowfly larva. In the locust and the stick insect and in the frog there are separate neurosecretory and ordinary motor endings but in the blowfly larva the characteristic features of motor and neurosecretory endings are combined in the same axon. The apparent sites of release of neurosecretory material show a characteristically rippled plasma membrane and are covered by only a flimsy layer of connective tissue material (stroma). In all three insects studied most of the neurosecretory material appears to be liberated into the haemolymph. Neurosecretory material appears to be released through the membrane at any point however, including, in the locust and in the blowfly larva, that part applied to the muscle. In the stick insect no endings have been seen as closely associated with the muscle as in the other two species. In the frog, as in the stick insect, the neurosecretory material is not liberated directly on to the muscle but into the connective tissue that lies between muscle fibres.Supported by a grant from the Science Research Council.Commonwealth Foundation Research Scholar.