Insect neurometamorphosis. III. Nerve cord shortening in a moth, galleria mellonella (L.), may be accomplished by humoral potentiation of neuroglial motility

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Abstract
Nerve cord segments were removed from last stage larvae and pharate pupae and transplanted into recipients of known developmental age. When transplanted into larvae the connectives shortened maximally in near‐synchrony with their host's counterpart; in both, potentiation began during early pupal development, and was completed 1.5–2.5 days after ecdysis. Histological comparisons revealed metamorphic changes in transplants, changes which paralleled those normally occurring in situ. Shortening of transplanted segments is not adventitious, and it would seem that shortening of the transplant and the host's counterpart are manifestations of the same phenomenon.Larval connectives transplanted into pupae younger than two days shorten completely; those transplanted into pupae aged two days or older, or into adults, do not. Actively shortening connectives shorten completely when transplanted into pupae two days old, or into younger pupae, but not when transplanted into larvae, or into pupae three or more days old. This affirms a critical period in the early pupa when activation is maximal. The nature and source of the potentiating factors are unknown, but most likely they are blood‐borne.Connectives with cauterized ganglia will shorten even though axon degeneration is pronounced. This shortening, too, is potentiated during the critical period. The hypothesis is advanced that humoral factors may be potentiating shortening by activating neuroglial motility.Connectives which shorten slightly in situ will shorten entirely if transplanted into hosts in the critical period. The inhibition removed by the operation may be mechanical, since connectives which shorten in situ are located in body segments which also shorten.