Acetylcholine as a Growth Factor in Early Larval Development of the Silkworm

Abstract

ACETYLCHOLINE is required in the diet of silkworm larvae for normal moulting to occur. On a semi-synthetic basal diet (Table 1, No. 4) the newly hatched larvae die after about 14 days without further moult. In tests each using twenty larvae, it was found that the diet containing mulberry leaves (diet 1, ref. 1) yielded 100 per cent successful moult to second instar with a larval weight of 5.4 mg each; the diet with defatted soybean^2,3 and no other important adjuvants (diet 2) yielded 80 per cent moult (4.5 mg); the diet with royal jelly⁴ (diet 3) yielded 100 per cent moult (5.85 mg); the basal diet without adjuvants (diet 4) yielded no moult; the basal diet with royal jelly (diet 5) yielded 70 per cent moult (4.8 mg); and basal diet plus acetylcholine (diet 6) yielded 80 per cent moult (4.0 mg). From these results one observes that royal jelly increases moulting and larval weight. Royal jelly contains large amounts of acetylcholine^5,6. A watersoluble, low-molecular-weight, dialysable fraction of royal jelly also provided similar growth stimulation. We therefore added acetylcholine to the diet⁷ expecting the same results as with royal jelly (diet 6). As described here, acetylcholine can replace royal jelly in stimulating moulting of the larvae.