Abstract
An experimental study was made of the effects of the growth hormone, produced by the neurosecretory Light Green Cells (LGC) of the cerebral ganglia, on shell calcification in the freshwater snail Lymnaea stagnalis. LGC removal had no effects on the concentration of calcium in the shell and the shell edge nor in the soft body parts with the exception of the mantle edge: In this tissue, 21 days after the operation, it was 30% lower than normal. In control as well as in -LGC snails, the half-life of 47Ca, injected into the hemolymph, was less than or equal to 5 min. For 5–30 min after the injection no increase was observed in the specific activity of the mantle edge, the mantle, and the other soft body parts. On the other hand, the shell edge showed a continuous increase in specific activity, but that in -LGC snails was significantly lower (by 69–92%) than that in the control snails. The labeling of the shell did not show this increase and was not affected by LGC removal. It is concluded that, with regard to shell growth, the growth hormone acts specifically on the mantle edge; it stimulates the formation of the outer crystalline layer and probably also the periostracum.
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